# Camera Protocol

The camera protocol v2 is used to configure camera payloads and request their status.
It provides basic methods for photo capture, video capture and streaming, setting zoom and focus, querying and configuring camera storage, and selecting multiple cameras.
It also defines a camera definition file format that allows a GCS to generate a configuration UI for setting any property of the camera using parameters.

:::info
This protocol supersedes [Camera Protocol v1 (Simple Trigger Protocol)](../services/camera_v1.md).
The older protocol enables camera triggering, but does not support other features or querying camera capabilities.
:::

:::warning
We are transitioning from specific request commands to a single generic requestor.
GCS and MAVLink SDKs/apps should support both approaches as we migrate to exclusive use of the new method (documented here).
For more information see [Migration Notes for GCS & Camera Servers](#migration-notes-for-gcs--mavlink-sdks).
:::

## MAVLink Camera Implementations

Camera Managers provide a MAVLink Camera protocol interface for cameras that don't directly implement MAVLink support.
These generally run on a companion computer:

- [MAVLink Camera Manager](https://github.com/mavlink/mavlink-camera-manager) (actively maintained)
- [Dronecode Camera Manager](https://camera-manager.dronecode.org/en/)
- [SIYI A8 mini camera manager](https://github.com/julianoes/siyi-a8-mini-camera-manager) - MAVSDK-plugin based camera manager for the [SIYI A8 mini](https://shop.siyi.biz/products/siyi-a8-mini) (includes tutorial).

These cameras have inbuilt support for MAVLink (but not necessarily camera protocol v2):

- [PhaseOne Cameras](https://geospatial.phaseone.com/) ([source](https://geospatial.phaseone.com/resources-support/developer/mavlink/)).
- [Workswell cameras](https://www.drone-thermal-camera.com/): WIRIS Pro, WIRIS Pro SC, WIRIS Security, WIRIS Agro, GIS-320 ([source](https://www.drone-thermal-camera.com/mavlink-interface-for-uav-cameras/)).

### 相机连接

MAVLink cameras are identified and addressed by their system and component id.

Components that have non-MAVLink cameras attached, such as companion computers, are expected to expose each of them as a separate MAVLink camera component with its own `HEARTBEAT`.

The exception is the _autopilot_ component, which can "proxy" up to 6 attached non-MAVLink cameras: these are identified by a `camera_device_id` field in messages and `Target Camera ID` label in commands.

#### Camera Messages

All MAVLink components include their system id and component id fields in the [MAVLink packet header](../guide/serialization.md#mavlink2_packet_format) when sending messages.
As each MAVLink camera component (with [HEARTBEAT.type=MAV_TYPE_CAMERA](../messages/common.md#HEARTBEAT)) represents just one camera, these ids can be used to uniquely identify the camera associated with a message.

non-MAVLink cameras attached to the autopilot are identified first by the autopilot system/component id, and then by a `camera_device_id` field in the message payload (all camera messages should have an id field with this or a similar name).
An autopilot should set this to the id of the associated camera device, and otherwise this should always be set to zero.

#### Camera Addressing in Commands

MAVLink cameras are sent commands addressed using their system and component ids (just as when addressing commands to any other component).

To send commands to autopilot-attached cameras, the command should be send to the autopilot component.
The device id of the target attached camera must further be set in the command's `Target Camera ID` parameter (the index and precise label of this parameter may vary).
The autopilot is required to respond to the command with `COMMAND_ACK`, populating the [COMMAND_ACK.result_param2](../messages/common.md#COMMAND_ACK) field with the id of the targeted autopilot connected camera, if any.

Note that the `Target Camera ID` parameter should be set to `0` in order to target all cameras, or if targeting a MAVLink camera.

#### Camera Addressing in Missions

When using a camera MAV_CMD in a mission, the `id` parameter (if present) indicates the target camera:

- 1 - 6 indicates a flight-stack connected camera
- 7-255 is the component id of a MAVLink connected camera.
  Note that component ids 1-6 should never be used for MAVLink cameras!
- 0 indicates "all connected cameras".

When processing a camera item in a mission the autopilot should:

- For `Target Camera ID` values of `1`-`6`, perform the specified camera action on the connected camera if it exists, and otherwise log an error.
- For other `Target Camera ID` values, re-emit the `MAV_CMD` using the command protocol, setting the target component id to the `id` set in the camera mission item.
  It should also log any errors from the returned `COMMAND_ACK`.

:::info
Flight stacks that predate using a camera id typically re-emit the mission command addressed either to the broadcast component id (`0`) or to [MAV_COMP_ID_CAMERA](../messages/common.md#MAV_COMP_ID_CAMERA).
The former triggers all cameras on the system, while the later provides better command handling because there is only one `COMMAND_ACK`.
:::

## The camera identification operation identifies all the available cameras and determines their capabilities.

### Connection

MAVLink Camera components are expected to follow the [Heartbeat/Connection Protocol](../services/heartbeat.md) and sent a constant flow of heartbeats (nominally at 1Hz).
Cameras must set a [HEARTBEAT.type](../messages/common.md#HEARTBEAT) of [MAV_TYPE_CAMERA](../messages/common.md#MAV_TYPE_CAMERA).
Each camera must use a different pre-defined camera component ID.
Values of [MAV_COMP_ID_CAMERA](../messages/common.md#MAV_COMP_ID_CAMERA) to [MAV_COMP_ID_CAMERA6](../messages/common.md#MAV_COMP_ID_CAMERA6) are recommended, but in theory any camera ID may be used except for 0 to 6 (which are reserved for cameras proxied by another component, such as the autopilot).

A GCS should start the [Camera Identification](#camera_identification) process the first time it detects a `HEARTBEAT` from a new:

- MAVLink camera component.
- Autopilot, in order to detect autopilot-connected cameras.

:::info
If a receiving system stops receiving heartbeats from the camera it is assumed to be _disconnected_, and should be removed from the list of available cameras.
If heartbeats are again detected, the _camera identification_ process below must be restarted from the beginning.
:::

:::info
If a vehicle has more than one MAVLink camera, each camera will have a different component ID and send its own heartbeat.
The vehicle autopilot might also have directly connected cameras, which are separately addressed by a camera device id.
The GCS should create multiple instances of a camera controller based on the component ID of each camera, and also the component ID of the autopilot and each of its attached camera devices.
All commands are sent to a specific camera by addressing the command to a specific component ID, and additionally the camera device id for autopilots.
:::

### Camera Identification {#camera_identification}

The camera identification operation identifies all the available cameras associated with a system and determines their capabilities.
It is used to discover both MAVLink cameras and non-MAVLink cameras attached to the autopilot.

The process involves requesting the [CAMERA_INFORMATION](../messages/common.md#CAMERA_INFORMATION) message from autopilots and MAVLink cameras as they are discovered.
`CAMERA_INFORMATION.flags` provides information about camera capabilities.
It contains a bitmap of [CAMERA_CAP_FLAGS](../messages/common.md#CAMERA_CAP_FLAGS) values that tell the GCS if the camera supports still image capture, video capture, or video streaming, and if it needs to be in a certain mode for capture, etc.

:::tip
Camera identification must be carried out before all other camera operations!
:::

The first time a heartbeat is received from a new camera component ([HEARTBEAT.type=MAV_TYPE_CAMERA](../messages/common.md#MAV_TYPE_CAMERA)), the GCS should send it a [MAV_CMD_REQUEST_MESSAGE](../messages/common.md#MAV_CMD_REQUEST_MESSAGE) message asking for [CAMERA_INFORMATION](../messages/common.md#CAMERA_INFORMATION) (message id 259).
The camera will then respond with the a [COMMAND_ACK](../messages/common.md#COMMAND_ACK) message containing a result.
On success (result is [MAV_RESULT_ACCEPTED](../messages/common.md#MAV_RESULT_ACCEPTED)) the camera component must then send a [CAMERA_INFORMATION](../messages/common.md#CAMERA_INFORMATION) message.

[![Mermaid Sequence: Camera Type](https://mermaid.ink/img/pako:eNp9kVFLwzAYRf9KyJPCFBR8sOIgpnEOl3Y2mSBWSmi_anBNapsKY-y_L2tVnMLyFJJz8t1w1zi3BeAAt_DRgckh1Oq1UdVVapBftWqcznWtjEMTKv4fcvI40-YdUVVBo4b7_bOT8dibAbpjJJE3jEj07FY1BDssk09zllHCWUJeBtmz3th_YmApD7OEPSyYkBlnQpAJO_JRVHV2fX5xefxb7wcK53MipyuwnTuUjMackyjMCL0fsMg6QPYTmj_CqMenZR8nYWIxk16ibC5ZiFowBdKmtKcHZ_V_zabRbZxwIqdxhEfYA5XShW9hvXNT7N6gghQHfltAqbqlS3FqNh7t6kI5YIV2tsFBqZYtjLDqnBUrk-PANR18Q19N_lDQS3you299swXuYKDj?type=png)](https://mermaid-js.github.io/mermaid-live-editor/edit#pako:eNp9kVFLwzAYRf9KyJPCFBR8sOIgpnEOl3Y2mSBWSmi_anBNapsKY-y_L2tVnMLyFJJz8t1w1zi3BeAAt_DRgckh1Oq1UdVVapBftWqcznWtjEMTKv4fcvI40-YdUVVBo4b7_bOT8dibAbpjJJE3jEj07FY1BDssk09zllHCWUJeBtmz3th_YmApD7OEPSyYkBlnQpAJO_JRVHV2fX5xefxb7wcK53MipyuwnTuUjMackyjMCL0fsMg6QPYTmj_CqMenZR8nYWIxk16ibC5ZiFowBdKmtKcHZ_V_zabRbZxwIqdxhEfYA5XShW9hvXNT7N6gghQHfltAqbqlS3FqNh7t6kI5YIV2tsFBqZYtjLDqnBUrk-PANR18Q19N_lDQS3you299swXuYKDj)

<!-- Original diagram
sequenceDiagram;
    participant GCS
    participant MAVLink Camera
    MAVLink Camera->>GCS: HEARTBEAT [type: MAV_TYPE_CAMERA]
    GCS->>MAVLink Camera: MAV_CMD_REQUEST_MESSAGE(param1=259)
    GCS->>GCS: Start timeout
    MAVLink Camera->>GCS: COMMAND_ACK
    Note over MAVLink Camera,GCS: If MAV_RESULT_ACCEPTED send info.
    MAVLink Camera->>GCS: CAMERA_INFORMATION
-->

The operation follows the normal [Command Protocol](../services/command.md) rules for command/acknowledgment (if no `COMMAND_ACK` response is received for `MAV_CMD_REQUEST_MESSAGE` the command will be re-sent a number of times before failing).
If `CAMERA_INFORMATION` is not received after receiving an ACK with `MAV_RESULT_ACCEPTED`, the protocol assumes the message was lost, and the cycle of sending `MAV_CMD_REQUEST_MESSAGE` is repeated.
If `CAMERA_INFORMATION` is still not received after three cycle repeats, the GCS may assume that the camera is not supported.

The first time a heartbeat is received from an autopilot, the GCS follow the same process to query for information about directly connected cameras.
The only difference is that the autopilot should return a `CAMERA_INFORMATION` message for each connected camera, populated with its `camera_device_id`.

[![Mermaid Sequence: Autopilot](https://mermaid.ink/img/pako:eNqlkl9LwzAUxb9KyNMKczBBwcoGsY2zuLSzzXyxEkJzq4H1j206kOF3N2vnFGT4YJ6Se3_3nAO5O5xVCrCLW3jroMzA1_KlkcV1WiJ7atkYnelalgYtvOR3kXSmqvWmMkPr-Dybzy3vojtKYn5DCUdPWVEjrVzEyKPwIrYSgS_ImkerYBnx6TMa5bppjYMGJTttNY56hzHmi5g-rGnCBaNJQhZ0ZNPIYjo7v7hyfk727omxUZHRBVTdqYQ2CiOhjeLdD0RYGUDVFppvdtyTQd6HiGmyXnLLe3TFqY9aKBXSZV5NTjkQRmMigvA2ihnhQRSOMllAI4WCrc5AaDWbOn-YTyaTff8fFpcOHmNbK6RW9sN3e6kUm1coIMWuvSrIZbcxKU7LD4t2tZIGqNKmarCby00LYyytc_JeZtg1TQdf0GFpjhT0Q2zYrH7BPj4B4RLFGw?type=png)](https://mermaid-js.github.io/mermaid-live-editor/edit#pako:eNqlkl9LwzAUxb9KyNMKczBBwcoGsY2zuLSzzXyxEkJzq4H1j206kOF3N2vnFGT4YJ6Se3_3nAO5O5xVCrCLW3jroMzA1_KlkcV1WiJ7atkYnelalgYtvOR3kXSmqvWmMkPr-Dybzy3vojtKYn5DCUdPWVEjrVzEyKPwIrYSgS_ImkerYBnx6TMa5bppjYMGJTttNY56hzHmi5g-rGnCBaNJQhZ0ZNPIYjo7v7hyfk727omxUZHRBVTdqYQ2CiOhjeLdD0RYGUDVFppvdtyTQd6HiGmyXnLLe3TFqY9aKBXSZV5NTjkQRmMigvA2ihnhQRSOMllAI4WCrc5AaDWbOn-YTyaTff8fFpcOHmNbK6RW9sN3e6kUm1coIMWuvSrIZbcxKU7LD4t2tZIGqNKmarCby00LYyytc_JeZtg1TQdf0GFpjhT0Q2zYrH7BPj4B4RLFGw)

<!-- Original diagram
sequenceDiagram;
    participant GCS
    participant Autopilot
    Autopilot->>GCS: HEARTBEAT [cmp id: MAV_COMP_ID_AUTOPILOT1] (first)
    GCS->>Autopilot: MAV_CMD_REQUEST_MESSAGE(param1=259)
    GCS->>GCS: Start timeout
    Autopilot->>GCS: COMMAND_ACK
    Note over Autopilot,GCS: If MAV_RESULT_ACCEPTED send info.
    Autopilot->>GCS: CAMERA_INFORMATION(camera_device_id=1)
    Note over Autopilot,GCS: ...
    Autopilot->>GCS: CAMERA_INFORMATION(camera_device_id=6)
-->

#### Additional Camera Information

The `CAMERA_INFORMATION` response contains the bare minimum information about the camera and what it can or cannot do.
This is sufficient for basic image and/or video capture.

If a camera provides finer control over its settings `CAMERA_INFORMATION.cam_definition_uri` will include a URI to a [Camera Definition File](../services/camera_def.md).
If this URI exists, the GCS will request it, parse it and prepare the UI for the user to control the camera settings.

The `CAMERA_INFORMATION.cam_definition_version` field should provide a version for the definition file, allowing the GCS to cache it.
Once downloaded, it would only be requested again if the version number changes.

:::info
A GCS that implements this protocol is expected to support both HTTP (`http://`) and [MAVLink FTP](../services/ftp.md) (`mftp://`) URIs for download of the camera definition file.
If the camera provides an HTTP or MAVLink FTP interface, the definition file can be hosted on the camera itself.
Otherwise, it can be _hosted_ anywhere (on any reachable server).
:::

## 相机基本操作

### 相机捕获状态

Some cameras must be in a certain mode for still and/or video capture.

The GCS can determine if it needs to make sure the camera is in the proper mode prior to sending a start capture (image or video) command by checking whether the [CAMERA_CAP_FLAGS_HAS_MODES](../messages/common.md#CAMERA_CAP_FLAGS_HAS_MODES) bit is set true in [CAMERA_INFORMATION.flags](../messages/common.md#CAMERA_INFORMATION).

In addition, some cameras can capture images in any mode but with different resolutions.
For example, a 20 megapixel camera would take a full resolution image when set to `CAMERA_MODE_IMAGE` but only at the current video resolution if it is set to `CAMERA_MODE_VIDEO`.

To get the current mode, the GCS would send a [MAV_CMD_REQUEST_MESSAGE](../messages/common.md#MAV_CMD_REQUEST_MESSAGE) command asking for [CAMERA_SETTINGS](../messages/common.md#CAMERA_SETTINGS).
The camera component will then respond with the [COMMAND_ACK](../messages/common.md#COMMAND_ACK) message containing a result.
On success (`COMMAND_ACK.result` is [MAV_RESULT_ACCEPTED](../messages/common.md#MAV_RESULT_ACCEPTED)) the camera must then send a [CAMERA_SETTINGS](../messages/common.md#CAMERA_SETTINGS) message.
The current mode is the `CAMERA_SETTINGS.mode_id` field.

The sequence is shown below:

[![Camera Settings](https://mermaid.ink/img/eyJjb2RlIjoic2VxdWVuY2VEaWFncmFtO1xuICAgIHBhcnRpY2lwYW50IEdDU1xuICAgIHBhcnRpY2lwYW50IENhbWVyYVxuICAgIEdDUy0-PkNhbWVyYTogTUFWX0NNRF9SRVFVRVNUX01FU1NBR0UocGFyYW0xPTI2MClcbiAgICBHQ1MtPj5HQ1M6IFN0YXJ0IHRpbWVvdXRcbiAgICBDYW1lcmEtPj5HQ1M6IENPTU1BTkRfQUNLXG4gICAgTm90ZSBvdmVyIENhbWVyYSxHQ1M6IElmIE1BVl9SRVNVTFRfQUNDRVBURUQgc2VuZCBpbmZvLlxuICAgIENhbWVyYS0-PkdDUzogQ0FNRVJBX1NFVFRJTkdTIiwibWVybWFpZCI6eyJ0aGVtZSI6ImRlZmF1bHQifSwidXBkYXRlRWRpdG9yIjpmYWxzZX0)](https://mermaid-js.github.io/mermaid-live-editor/#/edit/eyJjb2RlIjoic2VxdWVuY2VEaWFncmFtO1xuICAgIHBhcnRpY2lwYW50IEdDU1xuICAgIHBhcnRpY2lwYW50IENhbWVyYVxuICAgIEdDUy0-PkNhbWVyYTogTUFWX0NNRF9SRVFVRVNUX01FU1NBR0UocGFyYW0xPTI2MClcbiAgICBHQ1MtPj5HQ1M6IFN0YXJ0IHRpbWVvdXRcbiAgICBDYW1lcmEtPj5HQ1M6IENPTU1BTkRfQUNLXG4gICAgTm90ZSBvdmVyIENhbWVyYSxHQ1M6IElmIE1BVl9SRVNVTFRfQUNDRVBURUQgc2VuZCBpbmZvLlxuICAgIENhbWVyYS0-PkdDUzogQ0FNRVJBX1NFVFRJTkdTIiwibWVybWFpZCI6eyJ0aGVtZSI6ImRlZmF1bHQifSwidXBkYXRlRWRpdG9yIjpmYWxzZX0)

<!-- Original sequence
sequenceDiagram;
    participant GCS
    participant Camera
    GCS->>Camera: MAV_CMD_REQUEST_MESSAGE(param1=260)
    GCS->>GCS: Start timeout
    Camera->>GCS: COMMAND_ACK
    Note over Camera,GCS: If MAV_RESULT_ACCEPTED send info.
    Camera->>GCS: CAMERA_SETTINGS
-->

:::info
Command acknowledgment and message resending is handled in the same way as for [camera identification](#camera_identification) (if a successful ACK is received the camera will expect the `CAMERA_SETTINGS` message, and repeat the cycle - up to 3 times - until it is received).
:::

To set the camera to a specific mode, the GCS would send the [MAV_CMD_SET_CAMERA_MODE](../messages/common.md#MAV_CMD_SET_CAMERA_MODE) command with the appropriate mode.

The sequence is shown below:

[![](https://mermaid.ink/img/eyJjb2RlIjoic2VxdWVuY2VEaWFncmFtO1xuICAgIHBhcnRpY2lwYW50IEdDU1xuICAgIHBhcnRpY2lwYW50IENhbWVyYVxuICAgIEdDUy0-PkNhbWVyYTogTUFWX0NNRF9TRVRfQ0FNRVJBX01PREVcbiAgICBHQ1MtPj5HQ1M6IFN0YXJ0IHRpbWVvdXRcbiAgICBDYW1lcmEtPj5HQ1M6IENPTU1BTkRfQUNLXG4gICAgTm90ZSBvdmVyIENhbWVyYSxHQ1M6IElmIE1BVl9SRVNVTFRfQUNDRVBURUQsIG1vZGUgd2FzIGNoYW5nZWQuIiwibWVybWFpZCI6eyJ0aGVtZSI6ImRlZmF1bHQifSwidXBkYXRlRWRpdG9yIjpmYWxzZX0)](https://mermaid-js.github.io/mermaid-live-editor/#/edit/eyJjb2RlIjoic2VxdWVuY2VEaWFncmFtO1xuICAgIHBhcnRpY2lwYW50IEdDU1xuICAgIHBhcnRpY2lwYW50IENhbWVyYVxuICAgIEdDUy0-PkNhbWVyYTogTUFWX0NNRF9TRVRfQ0FNRVJBX01PREVcbiAgICBHQ1MtPj5HQ1M6IFN0YXJ0IHRpbWVvdXRcbiAgICBDYW1lcmEtPj5HQ1M6IENPTU1BTkRfQUNLXG4gICAgTm90ZSBvdmVyIENhbWVyYSxHQ1M6IElmIE1BVl9SRVNVTFRfQUNDRVBURUQsIG1vZGUgd2FzIGNoYW5nZWQuIiwibWVybWFpZCI6eyJ0aGVtZSI6ImRlZmF1bHQifSwidXBkYXRlRWRpdG9yIjpmYWxzZX0)

<!-- Original sequence
sequenceDiagram;
    participant GCS
    participant Camera
    GCS->>Camera: MAV_CMD_SET_CAMERA_MODE
    GCS->>GCS: Start timeout
    Camera->>GCS: COMMAND_ACK
    Note over Camera,GCS: If MAV_RESULT_ACCEPTED, mode was changed.
-->

:::info
The operation follows the normal [Command Protocol](../services/command.md) rules for command/acknowledgment.
:::

### 存储状态

Before capturing images and/or videos, a GCS should query the storage status to determine if the camera has enough free space for these operations (and provide the user with feedback as to the current storage status).
The GCS will send the [MAV_CMD_REQUEST_MESSAGE](../messages/common.md#MAV_CMD_REQUEST_MESSAGE) command and it expects a [COMMAND_ACK](../messages/common.md#COMMAND_ACK) message back as well as a [STORAGE_INFORMATION](../messages/common.md#STORAGE_INFORMATION) response.
For formatting (or erasing depending on your implementation), the GCS will send a [MAV_CMD_STORAGE_FORMAT](../messages/common.md#MAV_CMD_STORAGE_FORMAT) command.

### Status

In addition to querying about storage status, the GCS should also request a stream of `CAMERA_CAPTURE_STATUS` messages in order to provide the user with proper UI indicators.

This can be done by sending a [MAV_CMD_SET_MESSAGE_INTERVAL](../messages/common.md#MAV_CMD_SET_MESSAGE_INTERVAL) command asking for [CAMERA_CAPTURE_STATUS](../messages/common.md#CAMERA_CAPTURE_STATUS).
The command it expects a [COMMAND_ACK](../messages/common.md#COMMAND_ACK) message back and then [CAMERA_CAPTURE_STATUS](../messages/common.md#CAMERA_CAPTURE_STATUS) should be streamed at the specified rate.

### 静态图像捕获

A camera supports _still image capture_ if the [CAMERA_CAP_FLAGS_CAPTURE_IMAGE](../messages/common.md#CAMERA_CAP_FLAGS_CAPTURE_IMAGE) bit is set in [CAMERA_INFORMATION.flags](../messages/common.md#CAMERA_INFORMATION).

A GCS/MAVLink app uses the [MAV_CMD_IMAGE_START_CAPTURE](../messages/common.md#MAV_CMD_IMAGE_START_CAPTURE) command to request that the camera capture a specified number of images (or forever), and the duration between them.
The camera immediately returns the normal command acknowledgment ([MAV_RESULT](../messages/common.md#MAV_RESULT_ACCEPTED)).

Each time an image is captured, the camera _broadcasts_ a [CAMERA_IMAGE_CAPTURED](../messages/common.md#CAMERA_IMAGE_CAPTURED) message.
This message not only tells the GCS the image was captured, it is also intended for geo-tagging.

:::info
The camera must iterate `CAMERA_IMAGE_CAPTURED.image_index` and the counter used in `CAMERA_CAPTURE_STATUS.image_count` for every _new_ image capture (these values iterate until explicitly cleared using [MAV_CMD_STORAGE_FORMAT](#MAV_CMD_STORAGE_FORMAT)).
The index and total image count can be used to [re-request missing images](#missing_images) (e.g. images captured when the vehicle was out of telemetry range).
:::

The [MAV_CMD_IMAGE_STOP_CAPTURE](../messages/common.md#MAV_CMD_IMAGE_STOP_CAPTURE) command can optionally be sent to stop an image capture sequence (this is needed if image capture has been set to continue forever).

The still image capture message sequence _for missions_ (as described above) is shown below:

[![Mermaid Sequence: Image capture](https://mermaid. )](https://mermaid-js.github.io/mermaid-live-editor/# )

<!-- Original sequence
sequenceDiagram;
    participant GCS
    participant Camera
    GCS->>Camera: MAV_CMD_IMAGE_START_CAPTURE (interval, count/forever)
    GCS->>GCS: Start timeout
    Camera->>GCS: MAV_RESULT_ACCEPTED
    Note over Camera,GCS: Camera start capture of "count" images at "interval"
    Camera->>GCS: CAMERA_IMAGE_CAPTURED  (broadcast)
    Camera->>GCS: ...
    Camera->>GCS: CAMERA_IMAGE_CAPTURED (broadcast)
    Note over Camera,GCS: (Optional) Stop capture
    GCS->>Camera: MAV_CMD_IMAGE_STOP_CAPTURE
    GCS->>GCS: Start timeout
    Camera->>GCS: MAV_RESULT_ACCEPTED
-->

The message sequence for _interactive user-initiated image capture_ through a GUI is slightly different.
In this case the GCS should:

- Confirm that the camera is _ready_ to take images before allowing the user to request image capture.
  - It does this by sending [MAV_CMD_REQUEST_MESSAGE](../messages/common.md#MAV_CMD_REQUEST_MESSAGE) asking for [CAMERA_CAPTURE_STATUS](../messages/common.md#CAMERA_CAPTURE_STATUS).
  - The camera should return a `MAV_RESULT` and then [CAMERA_CAPTURE_STATUS](../messages/common.md#CAMERA_CAPTURE_STATUS).
  - The GCS should check that the status is "Idle" before enabling camera capture in the GUI.
- Send [MAV_CMD_IMAGE_START_CAPTURE](../messages/common.md#MAV_CMD_IMAGE_START_CAPTURE) specifying a single image (only).

The sequence is as shown below:

[![Mermaid Sequence: Interactive user initiated image capture](https://mermaid. )](https://mermaid-js.github.io/mermaid-live-editor/# )

<!-- Original sequence
sequenceDiagram;
    participant GCS
    participant Camera
    GCS->>Camera: MAV_CMD_REQUEST_MESSAGE(param1=262)
    GCS->>GCS: Start timeout
    Camera->>GCS: MAV_RESULT_ACCEPTED
    GCS->>GCS: Start timeout
    Camera->>GCS: CAMERA_CAPTURE_STATUS (status)
    Note over Camera,GCS: Repeat until status is IDLE
    GCS->>Camera: MAV_CMD_IMAGE_START_CAPTURE (interval, count/forever)
    GCS->>GCS: Start timeout
    Camera->>GCS: MAV_RESULT_ACCEPTED
    Note over Camera,GCS: Camera start capture of 1 image
    GCS->>GCS: Start timeout
    Camera->>GCS: CAMERA_IMAGE_CAPTURED  (broadcast)
-->

### Request Lost CAMERA_IMAGE_CAPTURED Messages {#missing_images}

The camera broadcasts a [CAMERA_IMAGE_CAPTURED](#CAMERA_IMAGE_CAPTURED) every time a new image is captured, iterating both the current image index (`CAMERA_IMAGE_CAPTURED.image_index`) and the total image count (`CAMERA_CAPTURE_STATUS.image_count`).

These messages can be lost during transmission; for example if the vehicle is out of data-link range of the ground stations.

Lost image capture messages can be detected by comparing GCS and camera image counts.
Individual entries can be requested using [MAV_CMD_REQUEST_MESSAGE](../messages/common.md#MAV_CMD_REQUEST_MESSAGE), where `param1="MAVLINK_MSG_ID_CAMERA_IMAGE_CAPTURED"` and `param2="the index of the missing image"`.

The camera image log iterates "forever" (but may be explicitly reset using [MAV_CMD_STORAGE_FORMAT.param3=1](../messages/common.md#MAV_CMD_STORAGE_FORMAT)).

### Video Capture

A camera supports video capture if the [CAMERA_CAP_FLAGS_CAPTURE_VIDEO](../messages/common.md#CAMERA_CAP_FLAGS_CAPTURE_VIDEO) bit is set in [CAMERA_INFORMATION.flags](../messages/common.md#CAMERA_INFORMATION).

To start recording videos, the GCS uses the [MAV_CMD_VIDEO_START_CAPTURE](../messages/common.md#MAV_CMD_VIDEO_START_CAPTURE) command.
If requested, the [CAMERA_CAPTURE_STATUS](#CAMERA_CAPTURE_STATUS) message is sent to the GCS at a set interval.

To stop recording, the GCS uses the [MAV_CMD_VIDEO_STOP_CAPTURE](../messages/common.md#MAV_CMD_VIDEO_STOP_CAPTURE) command.

### Video Streaming {#video_streaming}

:::info
The GCS should already have identified all connected cameras by their heartbeat and followed the [Camera Identification](#camera_identification) steps to get [CAMERA_INFORMATION](../messages/common.md#CAMERA_INFORMATION) for every camera.
:::

A camera is capable of streaming video if it sets the [CAMERA_CAP_FLAGS_HAS_VIDEO_STREAM](../messages/common.md#CAMERA_CAP_FLAGS_HAS_VIDEO_STREAM) bit set in [CAMERA_INFORMATION.flags](../messages/common.md#CAMERA_INFORMATION).

The sequence for requesting _all_ video streams from a particular camera is shown below:

[![Mermaid Sequence: Video stream info](https://mermaid. )](https://mermaid-js.github.io/mermaid-live-editor/# )

<!-- Original sequence
sequenceDiagram;
    participant GCS
    participant Camera
    Note over GCS,Camera: IF CAMERA_CAP_FLAGS_HAS_VIDEO_STREAM<br>in CAMERA_INFORMATION.flags<br>request all streams.
    GCS->>Camera: MAV_CMD_REQUEST_MESSAGE(param1=269,param2=0)
    GCS->>GCS: Start timeout
    Camera->>GCS: MAV_RESULT_ACCEPTED
    Note over Camera,GCS: Camera sends information for<br> all streams.
    Camera->>GCS: VIDEO_STREAM_INFORMATION (1)
    Camera->>GCS: ...
    Camera->>GCS: VIDEO_STREAM_INFORMATION (n)
-->

The steps are:

1. GCS follows the [Camera Identification](#camera_identification) steps to get [CAMERA_INFORMATION](../messages/common.md#CAMERA_INFORMATION) for every camera.

2. GCS checks if [CAMERA_INFORMATION.flags](../messages/common.md#CAMERA_INFORMATION) contains the [CAMERA_CAP_FLAGS_HAS_VIDEO_STREAM](../messages/common.md#CAMERA_CAP_FLAGS_HAS_VIDEO_STREAM) flag.

3. If so, the GCS sends the [MAV_CMD_REQUEST_MESSAGE](../messages/common.md#MAV_CMD_REQUEST_MESSAGE) message to the camera requesting the video streaming configuration (`param1=269`) for all streams (`param2=0`).

   ::: info
   A GCS can also request information for a _particular stream_ by setting its id in `param2`.
   :::

4. Camera returns a [VIDEO_STREAM_INFORMATION](../messages/common.md#VIDEO_STREAM_INFORMATION) message for the specified stream or all streams it supports.

:::info
If your camera only provides video streaming and nothing else (no camera features), the [CAMERA_CAP_FLAGS_HAS_VIDEO_STREAM](../messages/common.md#CAMERA_CAP_FLAGS_HAS_VIDEO_STREAM) flag is the only flag you need to set.
The GCS will then provide video streaming support and skip camera control.
:::

### Video Metadata

The protocol provides some information about video streaming support in [CAMERA_CAP_FLAGS](#CAMERA_CAP_FLAGS), such as support for video streaming (`CAMERA_CAP_FLAGS_HAS_VIDEO_STREAM`) and thermal range information (`CAMERA_CAP_FLAGS_HAS_THERMAL_RANGE`),
In addition the [VIDEO_STREAM_INFORMATION](#VIDEO_STREAM_INFORMATION) and [VIDEO_STREAM_STATUS](#VIDEO_STREAM_STATUS) provide broad information about each stream, including its transport mechanism, encoding, resolution, frame rate, and status ([VIDEO_STREAM_STATUS_FLAGS](#VIDEO_STREAM_STATUS_FLAGS)).

MAVLink does not specify any mechanism for getting frame-synchronized video metadata, such as absolute thermal values of thermal video streams, text-tracks, and so on.
The following sections outline some MAVLink-centric methods for getting "approximate" video-synchronized metadata.

#### Camera absolute thermal range

A thermal video stream is often coloured as a heatmap in order to highlight hotter and colder sections.
This heatmap is relative to the hottest and coldest points on the frame, so the hot sections are not necessarily hot, they are just hotter than their surroundings.
If you're searching for things that have a specific temperature, it can be useful to know the absolute temperatures represented by the image.

The [CAMERA_THERMAL_RANGE](#CAMERA_THERMAL_RANGE) message can be streamed alongside a video stream to provide this information.
The message includes the associated stream and camera id, along with the position and value of the maximum and minimum temperature in the video frame.
That is sufficient to overlay the hottest and coldest points on a video, and in theory to determine the absolute temperature of all pixels.

:::info
The message is streamed alongside the video stream, but there is no precise mechanism to synchronize values to frames.
The information is therefore an estimate/approximate.
:::

The message can be requested for a particular camera and stream using the [MAV_CMD_SET_MESSAGE_INTERVAL](#MAV_CMD_SET_MESSAGE_INTERVAL), when the associated [VIDEO_STREAM_STATUS.flag](#VIDEO_STREAM_STATUS) for the stream has bit [VIDEO_STREAM_STATUS_FLAGS_THERMAL_RANGE_ENABLED](#VIDEO_STREAM_STATUS_FLAGS_THERMAL_RANGE_ENABLED) set.
Note that `MAV_CMD_SET_MESSAGE_INTERVAL.param3` indicates the stream id of the current camera, or 0 for all streams, while `param4` indicates the target `camera_device_id` for autopilot-attached cameras or 0 for MAVLink cameras.

### 相机模式

A camera may support tracking a point and/or a rectangle.
Information about the tracked point can be streamed during tracking, and may be passed to a gimbal in order to move the camera to track the target (or control vehicle attitude to track the target).

Support for tracking different types of targets is indicated by the [CAMERA_CAP_FLAGS_HAS_TRACKING_POINT](../messages/common.md#CAMERA_CAP_FLAGS_HAS_TRACKING_POINT) and/or [CAMERA_CAP_FLAGS_HAS_TRACKING_RECTANGLE](../messages/common.md#CAMERA_CAP_FLAGS_HAS_TRACKING_RECTANGLE) flags in [CAMERA_INFORMATION.flags](../messages/common.md#CAMERA_INFORMATION).

To start camera tracking a GCS uses either the [MAV_CMD_CAMERA_TRACK_POINT](#MAV_CMD_CAMERA_TRACK_POINT) or [MAV_CMD_CAMERA_TRACK_RECTANGLE](#MAV_CMD_CAMERA_TRACK_RECTANGLE) command.

After starting camera tracking you should call [MAV_CMD_SET_MESSAGE_INTERVAL](../messages/common.md#MAV_CMD_SET_MESSAGE_INTERVAL) to start streaming the [CAMERA_TRACKING_IMAGE_STATUS](#CAMERA_TRACKING_IMAGE_STATUS) message at your desired rate.
This message contains information about the tracked point/rectangle in an image, and may be used by the receiving system to determine the location of the target (alongside other information like the [CAMERA_FOV_STATUS](#CAMERA_FOV_STATUS)).

If geo-tracking status information is supported (indicated by `CAMERA_CAP_FLAGS_HAS_TRACKING_GEO_STATUS`) you should also call [MAV_CMD_SET_MESSAGE_INTERVAL](../messages/common.md#MAV_CMD_SET_MESSAGE_INTERVAL) to stream [CAMERA_TRACKING_GEO_STATUS](#CAMERA_TRACKING_GEO_STATUS) at your desired rate.
This message provides the location of the target in physical co-ordinates that can be passed to a gimbal.

To stop any kind of tracking, a GCS uses the [MAV_CMD_CAMERA_STOP_TRACKING](#MAV_CMD_CAMERA_STOP_TRACKING) command.
After stopping tracking you should call `MAV_CMD_SET_MESSAGE_INTERVAL` to stop streaming `CAMERA_TRACKING_IMAGE_STATUS` and `CAMERA_TRACKING_GEO_STATUS` (set their rates to 0).

#### Camera tracking message sequence

:::info
The GCS should already have identified all connected cameras by their heartbeat and followed the [Camera Identification](#camera_identification) steps to get [CAMERA_INFORMATION](../messages/common.md#CAMERA_INFORMATION) for every camera.
:::

The sequence for tracking a point is shown below (tracking a rectangle is the same sequence but a different tracking command).

[![Mermaid Sequence: tracking info](https://mermaid.ink/img/pako: ?type=png)](https://mermaid.live/edit#pako: )

<!-- Original sequence
sequenceDiagram;
    participant GCS
    participant Camera
    Note over GCS,Camera: IF CAMERA_CAP_FLAGS_HAS_TRACKING_POINT<br>in CAMERA_INFORMATION.flags<br> start tracking point
    GCS->>Camera: MAV_CMD_CAMERA_TRACK_POINT( "point information" )
    Camera->>GCS: MAV_RESULT_ACCEPTED

    Note over GCS: Set streaming rate<br>CAMERA_TRACKING_IMAGE_STATUS
    GCS->>Camera: MAV_CMD_SET_MESSAGE_INTERVAL(param1=275,param2=10,param7=1)
    Camera->>GCS: MAV_RESULT_ACCEPTED
    Note over GCS: Set streaming rate CAMERA_TRACKING_GEO_STATUS<br>(support is assume here)
    GCS->>Camera: MAV_CMD_SET_MESSAGE_INTERVAL(param1=276,param2=10,param7=1)
    Camera->>GCS: MAV_RESULT_ACCEPTED

    Note over Camera,GCS: Camera streams tracking information (pass to gimbal)
    Camera->>GCS: CAMERA_TRACKING_IMAGE_STATUS (1)
    Camera->>GCS: CAMERA_TRACKING_GEO_STATUS (1)

    Camera->>GCS: ...
    Camera->>GCS: CAMERA_TRACKING_GEO_STATUS (n)
    Camera->>GCS: CAMERA_TRACKING_IMAGE_STATUS (n)

    Note over Camera,GCS: GCS stops tracking and streaming when ready
    GCS->>Camera: MAV_CMD_CAMERA_STOP_TRACKING (1)
    Camera->>GCS: MAV_RESULT_ACCEPTED
    GCS->>Camera: MAV_CMD_SET_MESSAGE_INTERVAL(param1=275,param2=0,param7=1)
    Camera->>GCS: MAV_RESULT_ACCEPTED
    GCS->>Camera: MAV_CMD_SET_MESSAGE_INTERVAL(param1=276,param2=0,param7=1)
    Camera->>GCS: MAV_RESULT_ACCEPTED
-->

The steps are:

1. GCS follows the [Camera Identification](#camera_identification) steps to get [CAMERA_INFORMATION](../messages/common.md#CAMERA_INFORMATION) for every camera.
2. GCS checks if [CAMERA_INFORMATION.flags](../messages/common.md#CAMERA_INFORMATION) contains the `CAMERA_CAP_FLAGS_HAS_TRACKING_RECTANGLE`, `CAMERA_CAP_FLAGS_HAS_TRACKING_POINT`, `CAMERA_CAP_FLAGS_HAS_TRACKING_GEO_STATUS`.
3. If tracking is supported the GCS sends the command to start the type of tracking it wants to do: [MAV_CMD_CAMERA_TRACK_POINT](#MAV_CMD_CAMERA_TRACK_POINT) or [MAV_CMD_CAMERA_TRACK_RECTANGLE](#MAV_CMD_CAMERA_TRACK_RECTANGLE).
   The sequence above just shows point tracking.
4. Set the desired rates (intervals) for streaming the tracking status messages.
5. Camera streams [CAMERA_TRACKING_IMAGE_STATUS](#CAMERA_TRACKING_IMAGE_STATUS) and/or [CAMERA_TRACKING_GEO_STATUS](#CAMERA_TRACKING_GEO_STATUS).
   These are used to provide camera targetting information.
6. To stop tracking, a GCS uses the [MAV_CMD_CAMERA_STOP_TRACKING](#MAV_CMD_CAMERA_STOP_TRACKING) command.
   The streaming intervals must also be set to zero.

### Battery Status

Camera components that are powered from their own battery should publish [BATTERY_STATUS](../messages/common.md#BATTERY_STATUS) messages.

Other components like a GCS will typically only use the camera `BATTERY_STATUS.battery_remaining` field (or possibly `time_remaining`); generally other fields can be set as "not supported".

## Message/Command/Enum Summary

### 消息

| 消息                                                                                                                                                                                         | 描述                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| <a id="CAMERA_INFORMATION"></a>[CAMERA_INFORMATION](../messages/common.md#CAMERA_INFORMATION)                                                                         | Basic information about camera including supported features and URI link to extended information (`cam_definition_uri` field).                                                                                                                                                                                                                                                                                                                                  |
| <a id="CAMERA_SETTINGS"></a>[CAMERA_SETTINGS](../messages/common.md#CAMERA_SETTINGS)                                                                                  | Timestamp and camera mode information.                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| <a id="VIDEO_STREAM_INFORMATION"></a>[VIDEO_STREAM_INFORMATION](../messages/common.md#VIDEO_STREAM_INFORMATION)                                  | Information defining a video stream configuration. If a camera has more than one video stream, it would send one of this for each video stream, with their specific configuration. Each stream must have its own, unique `stream_id`.                                                                                                                                                                                                              |
| <a id="VIDEO_STREAM_STATUS"></a>[VIDEO_STREAM_STATUS](../messages/common.md#VIDEO_STREAM_STATUS)                                                 | Information updating a video stream configuration. <!-- TBD? -->                                                                                                                                                                                                                                                                                                                                                                                                                   |
| <a id="storage_information"></a>[STORAGE_INFORMATION](../messages/common.md#STORAGE_INFORMATION)                                                                      | Storage information (e.g. number and type of storage devices, total/used/available capacity, read/write speeds).                                                                                                                                                                                                                                                                                                                |
| <a id="CAMERA_CAPTURE_STATUS"></a>[CAMERA_CAPTURE_STATUS](../messages/common.md#CAMERA_CAPTURE_STATUS)                                           | Camera capture status, including current capture type (if any), capture interval, available capacity.                                                                                                                                                                                                                                                                                                                                                           |
| <a id="CAMERA_IMAGE_CAPTURED"></a>[CAMERA_IMAGE_CAPTURED](../messages/common.md#CAMERA_IMAGE_CAPTURED)                                           | Information about image captured (returned to GCS every time an image is captured).                                                                                                                                                                                                                                                                                                                                                                             |
| <a id="CAMERA_FOV_STATUS"></a>[CAMERA_FOV_STATUS](../messages/common.md#CAMERA_FOV_STATUS)                                                       | Information about the field of view of a camera. Requested using [MAV_CMD_REQUEST_MESSAGE](#MAV_CMD_REQUEST_MESSAGE).                                                                                                                                                                                                                                                                               |
| <a id="CAMERA_TRACKING_IMAGE_STATUS"></a>[CAMERA_TRACKING_IMAGE_STATUS](../messages/common.md#CAMERA_TRACKING_IMAGE_STATUS) | Camera tracking status, sent while in active tracking. Use [MAV_CMD_SET_MESSAGE_INTERVAL](../messages/common.md#MAV_CMD_SET_MESSAGE_INTERVAL) to define message interval.                                                                                                                                                                                                      |
| <a id="CAMERA_TRACKING_GEO_STATUS"></a>[CAMERA_TRACKING_GEO_STATUS](../messages/common.md#CAMERA_TRACKING_GEO_STATUS)       | Camera tracking status, sent while in active tracking. Use [MAV_CMD_SET_MESSAGE_INTERVAL](../messages/common.md#MAV_CMD_SET_MESSAGE_INTERVAL) to define message interval.                                                                                                                                                                                                      |
| <a id="CAMERA_THERMAL_RANGE"></a>[CAMERA_THERMAL_RANGE](../messages/common.md#CAMERA_THERMAL_RANGE)                                              | Camera absolute thermal range. This provides value and position of max/min temperature in a video stream, allowing thermal range of video to be calibrated to absolute rather than relative temperature. Use [MAV_CMD_SET_MESSAGE_INTERVAL](../messages/common.md#MAV_CMD_SET_MESSAGE_INTERVAL) to define message interval for a particular camera and stream. |

### 命令

| Command                                                                                                                                                                                                               | 描述                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |   |
| <a id="MAV_CMD_REQUEST_MESSAGE"></a>[MAV_CMD_REQUEST_MESSAGE](../messages/common.md#MAV_CMD_REQUEST_MESSAGE)                                           | Send command to request any message (used to request [CAMERA_INFORMATION](#CAMERA_INFORMATION) and the other messages above)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
| <a id="MAV_CMD_SET_CAMERA_MODE"></a>[MAV_CMD_SET_CAMERA_MODE](../messages/common.md#MAV_CMD_SET_CAMERA_MODE)                      | Send command to set [CAMERA_MODE](#CAMERA_MODE).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
| <a id="MAV_CMD_SET_CAMERA_ZOOM"></a>[MAV_CMD_SET_CAMERA_ZOOM](../messages/common.md#MAV_CMD_SET_CAMERA_ZOOM)                      | Send command to set the camera zoom.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
| <a id="MAV_CMD_SET_CAMERA_FOCUS"></a>[MAV_CMD_SET_CAMERA_FOCUS](../messages/common.md#MAV_CMD_SET_CAMERA_FOCUS)                   | Send command to set the camera focus.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
| <a id="MAV_CMD_IMAGE_START_CAPTURE"></a>[MAV_CMD_IMAGE_START_CAPTURE](../messages/common.md#MAV_CMD_IMAGE_START_CAPTURE)          | Send command to start image capture, specifying the duration between captures and total number of images to capture.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
| <a id="MAV_CMD_IMAGE_STOP_CAPTURE"></a>[MAV_CMD_IMAGE_STOP_CAPTURE](../messages/common.md#MAV_CMD_IMAGE_STOP_CAPTURE)             | Send command to stop image capture.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| <a id="MAV_CMD_VIDEO_START_CAPTURE"></a>[MAV_CMD_VIDEO_START_CAPTURE](../messages/common.md#MAV_CMD_VIDEO_START_CAPTURE)          | Send command to start video capture, specifying the frequency that [CAMERA_CAPTURE_STATUS](#CAMERA_CAPTURE_STATUS) messages should be sent while recording.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
| <a id="MAV_CMD_VIDEO_STOP_CAPTURE"></a>[MAV_CMD_VIDEO_STOP_CAPTURE](../messages/common.md#MAV_CMD_VIDEO_STOP_CAPTURE)             | Send command to stop video capture.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| <a id="MAV_CMD_VIDEO_START_STREAMING"></a>[MAV_CMD_VIDEO_START_STREAMING](../messages/common.md#MAV_CMD_VIDEO_START_STREAMING)    | Send command to start video streaming for the given Stream ID (`stream_id`.) This is mostly for streaming protocols that _push_ a stream. If your camera uses a connection based streaming configuration (RTSP, TCP, etc.), you may ignore it if you don't need it but note that you still must ACK the command, like all `MAV_CMD_XXX` commands. When using a connection based streaming configuration, the GCS will connect the stream from its side. When a camera offers more than one stream and the user switches from one stream to another, the GCS will send a [MAV_CMD_VIDEO_STOP_STREAMING](../messages/common.md#MAV_CMD_VIDEO_STOP_STREAMING) command targeting the current Stream ID followed by a [MAV_CMD_VIDEO_START_STREAMING](../messages/common.md#MAV_CMD_VIDEO_START_STREAMING) targeting the newly selected Stream ID.   |
| <a id="MAV_CMD_VIDEO_STOP_STREAMING"></a>[MAV_CMD_VIDEO_STOP_STREAMING](../messages/common.md#MAV_CMD_VIDEO_STOP_STREAMING)       | Send command to stop video streaming for the given Stream ID (`stream_id`.) This is mostly for streaming protocols that _push_ a stream. If your camera uses a connection based streaming configuration (RTSP, TCP, etc.), you may ignore it if you don't need it but note that you still must ACK the command, like all `MAV_CMD_XXX` commands. When using a connection based streaming configuration, the GCS will disconnect the stream from its side. When a camera offers more than one stream and the user switches from one stream to another, the GCS will send a [MAV_CMD_VIDEO_STOP_STREAMING](../messages/common.md#MAV_CMD_VIDEO_STOP_STREAMING) command targeting the current Stream ID followed by a [MAV_CMD_VIDEO_START_STREAMING](../messages/common.md#MAV_CMD_VIDEO_START_STREAMING) targeting the newly selected Stream ID. |
| <a id="MAV_CMD_CAMERA_TRACK_POINT"></a>[MAV_CMD_CAMERA_TRACK_POINT](../messages/common.md#MAV_CMD_CAMERA_TRACK_POINT)             | Initate visual point tracking, if supported by the camera ([CAMERA_CAP_FLAGS_HAS_TRACKING_POINT](#CAMERA_CAP_FLAGS) is set).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
| <a id="MAV_CMD_CAMERA_TRACK_RECTANGLE"></a>[MAV_CMD_CAMERA_TRACK_RECTANGLE](../messages/common.md#MAV_CMD_CAMERA_TRACK_RECTANGLE) | Initiate visual rectangle tracking, if supported by the camera ([CAMERA_CAP_FLAGS_HAS_TRACKING_RECTANGLE](#CAMERA_CAP_FLAGS) is set).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| <a id="MAV_CMD_CAMERA_STOP_TRACKING"></a>[MAV_CMD_CAMERA_STOP_TRACKING](../messages/common.md#MAV_CMD_CAMERA_STOP_TRACKING)       | Stop camera tracking (as initiated using `MAV_CMD_CAMERA_TRACK_POINT` or `MAV_CMD_CAMERA_TRACK_RECTANGLE`).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |

#### Deprecated Commands

These commands have been deprecated, replaced by the generic requester command [MAV_CMD_REQUEST_MESSAGE](#MAV_CMD_REQUEST_MESSAGE)

| Command                                                                                                                                                                                                                                                                  | 描述                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
| ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |   |
| <a id="MAV_CMD_REQUEST_CAMERA_SETTINGS"></a>[MAV_CMD_REQUEST_CAMERA_SETTINGS](../messages/common.md#MAV_CMD_REQUEST_CAMERA_SETTINGS)                                                 | Send command to request [CAMERA_SETTINGS](#CAMERA_SETTINGS).                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
| <a id="MAV_CMD_REQUEST_CAMERA_INFORMATION"></a>[MAV_CMD_REQUEST_CAMERA_INFORMATION](../messages/common.md#MAV_CMD_REQUEST_CAMERA_INFORMATION)                                        | Send command to request [CAMERA_INFORMATION](#CAMERA_INFORMATION).                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
| <a id="MAV_CMD_REQUEST_VIDEO_STREAM_INFORMATION"></a>[MAV_CMD_REQUEST_VIDEO_STREAM_INFORMATION](../messages/common.md#MAV_CMD_REQUEST_VIDEO_STREAM_INFORMATION) | Send command to request [VIDEO_STREAM_INFORMATION](#VIDEO_STREAM_INFORMATION). This is sent once for each camera when a camera is detected and it has set the [CAMERA_CAP_FLAGS_HAS_VIDEO_STREAM](../messages/common.md#CAMERA_CAP_FLAGS_HAS_VIDEO_STREAM) flag within the [CAMERA_INFORMATION](../messages/common.md#CAMERA_INFORMATION) message `flags` field. |
| <a id="MAV_CMD_REQUEST_VIDEO_STREAM_STATUS"></a>[MAV_CMD_REQUEST_VIDEO_STREAM_STATUS](../messages/common.md#MAV_CMD_REQUEST_VIDEO_STREAM_STATUS)                | Send command to request [VIDEO_STREAM_STATUS](#VIDEO_STREAM_STATUS). This is sent whenever there is a mode change (when [MAV_CMD_SET_CAMERA_MODE](../messages/common.md#MAV_CMD_SET_CAMERA_MODE) is sent.) It allows the camera to update the stream configuration when a camera mode change occurs.                                                                    |
| <a id="MAV_CMD_REQUEST_STORAGE_INFORMATION"></a>[MAV_CMD_REQUEST_STORAGE_INFORMATION](../messages/common.md#MAV_CMD_REQUEST_STORAGE_INFORMATION)                                     | Send command to request [STORAGE_INFORMATION](#storage_information).                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
| <a id="MAV_CMD_REQUEST_CAMERA_CAPTURE_STATUS"></a>[MAV_CMD_REQUEST_CAMERA_CAPTURE_STATUS](../messages/common.md#MAV_CMD_REQUEST_CAMERA_CAPTURE_STATUS)          | Send command to request [CAMERA_CAPTURE_STATUS](#CAMERA_CAPTURE_STATUS).                                                                                                                                                                                                                                                                                                                                                                                                                                       |

### Enum

| Enum                                                                                                                                                                                       | 描述                                                                                                                                                                                                                                                                                                                              |
| ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| <a id="CAMERA_CAP_FLAGS"></a>[CAMERA_CAP_FLAGS](../messages/common.md#CAMERA_CAP_FLAGS)                                                          | Camera capability flags (Bitmap). For example: ability to capture images in video mode, support for survey mode etc. Received in [CAMERA_INFORMATION](#CAMERA_INFORMATION).                                             |
| <a id="CAMERA_MODE"></a>[CAMERA_MODE](../messages/common.md#CAMERA_MODE)                                                                                              | Camera mode (image, video, survey etc.). Received in [CAMERA_SETTINGS](#CAMERA_SETTINGS).                                                                                                                                               |
| <a id="VIDEO_STREAM_TYPE"></a>[VIDEO_STREAM_TYPE](../messages/common.md#VIDEO_STREAM_TYPE)                                                       | Type of stream - e.g. RTSP, MPEG. Received in [VIDEO_STREAM_INFORMATION](#VIDEO_STREAM_INFORMATION).                                                                                                                  |
| <a id="VIDEO_STREAM_STATUS_FLAGS"></a>[VIDEO_STREAM_STATUS_FLAGS](../messages/common.md#VIDEO_STREAM_TYPE)                  | Bitmap of stream status flags - e.g. zoom, thermal imaging, etc. Received in [VIDEO_STREAM_INFORMATION](#VIDEO_STREAM_INFORMATION).                                                                                   |
| <a id="CAMERA_TRACKING_STATUS_FLAGS"></a>[CAMERA_TRACKING_STATUS_FLAGS](../messages/common.md#CAMERA_TRACKING_STATUS_FLAGS) | Current tracking status. Received in [CAMERA_TRACKING_IMAGE_STATUS](#CAMERA_TRACKING_IMAGE_STATUS) amd [CAMERA_TRACKING_GEO_STATUS](#CAMERA_TRACKING_GEO_STATUS). |
| <a id="CAMERA_TRACKING_MODE"></a>[CAMERA_TRACKING_MODE](../messages/common.md#CAMERA_TRACKING_MODE)                                              | Current tracking mode. Received in [CAMERA_TRACKING_IMAGE_STATUS](#CAMERA_TRACKING_IMAGE_STATUS).                                                                                                                                |
| <a id="CAMERA_TRACKING_TARGET_DATA"></a>[CAMERA_TRACKING_TARGET_DATA](../messages/common.md#CAMERA_TRACKING_TARGET_DATA)    | Indicates how target data is encoded in image. Received in [CAMERA_TRACKING_IMAGE_STATUS](#CAMERA_TRACKING_IMAGE_STATUS).                                                                                                        |

## Migration Notes for GCS & MAVLink SDKs

The original definition of this protocol used specific commands to query for each type of information requested from the camera: [MAV_CMD_REQUEST_CAMERA_INFORMATION](../messages/common.md#MAV_CMD_REQUEST_CAMERA_INFORMATION) (for [CAMERA_INFORMATION](../messages/common.md#CAMERA_INFORMATION)), [MAV_CMD_REQUEST_CAMERA_SETTINGS](../messages/common.md#MAV_CMD_REQUEST_CAMERA_SETTINGS), [MAV_CMD_REQUEST_CAMERA_CAPTURE_STATUS](../messages/common.md#MAV_CMD_REQUEST_CAMERA_CAPTURE_STATUS),
[MAV_CMD_REQUEST_VIDEO_STREAM_INFORMATION](../messages/common.md#MAV_CMD_REQUEST_VIDEO_STREAM_INFORMATION), [MAV_CMD_REQUEST_STORAGE_INFORMATION](../messages/common.md#MAV_CMD_REQUEST_STORAGE_INFORMATION).

The latest version replaces all of these specific commands with the general requestor [MAV_CMD_REQUEST_MESSAGE](../messages/common.md#MAV_CMD_REQUEST_MESSAGE).

The transition works like this:

1. Cameras need to handle both approaches for now (i.e. support both new generic and old specific commands).
2. Ground stations will move from using the old specific commands to using both. They can try the new one and if they don't get an answer within a timeout they need to fall back to the previous command.
3. After the new commands have been established in servers and ground stations, the old specific commands may be removed from the implementations.
