ApsaraVideo Live:StartLiveMPUTask

By default, each application ID supports a maximum of 200 single-stream ingest tasks and 40 stream mixing and transcoding tasks. To increase the quota, submit a ticket.

Stream mixing task lifecycle

Start

• When a streamer starts streaming for the first time, you can call StartLiveMPUTask to start a bypass task.

  • If no users are in the channel, a "channel does not exist" error is returned.

  • The bypass stream is output only when a user starts stream ingest. If the user in a single-stream task does not ingest a stream, the bypass stream cannot be played.

  • For a stream mixing task, at least one user must be ingesting a stream for the bypass stream to be playable. The layout area for users who are not ingesting streams shows a black screen.

• You can record the bypass task status, task type, and task parameters on your business server.

  • Task status: Started, Stopped.

  • Task type: Single-stream, Stream mixing.

  • Task parameters: The latest input parameters. For example, after a successful call to UpdateLiveMPUTask, record the latest task parameters.

• In co-streaming or PK scenarios, if a task has been updated to a stream mixing task and the streamer unexpectedly leaves and then rejoins the channel, your business server can call StartLiveMPUTask to restart the stream mixing task based on the saved task type and parameters.

  • If the system has not automatically cleared the task before you start it, the task starts successfully.

  • If the system has not yet cleared the task, a Task already exists error code is returned.

End

• When a streamer leaves the channel, call StopLiveMPUTask to stop the bypass task.

• If all users in the task leave the channel and StopLiveMPUTask is not called, the system automatically stops the bypass task after 2 minutes.

QPS limits

The queries per second (QPS) limit for a single user for this API is 500 calls/second. If you exceed this limit, API calls are throttled. This may affect your business. We recommend that you call this API reasonably.

Layout and volume SEI

Example for a co-streaming scenario:

If there is only one streamer, the `stream` collection in the SEI information that the viewer receives contains information for only one member. If the streamer is in a co-streaming or PK session, the `stream` collection contains information for multiple members. For example, when streamer `streamer111` is streaming alone, the SEI frame format that the viewer receives is as follows:
{"canvas":{"w":1920,"h":1080,"bgnd":0},"stream":[{"uid":"streamer111","paneid":-1,"zorder":0,"x":0,"y":0,"w":0,"h":0,"type":0,"status":1,"muted":0,"vol":0,"vad":0}],"ver":"1.0.0.20220915","ts":1697696105170} When streamer `streamer111` is co-streaming with viewer `viewer222`, the SEI frame format that the viewer receives is as follows:
{"canvas":{"w":1920,"h":1080,"bgnd":0},"stream":[{"uid":"streamer111","paneid":0,"zorder":1,"x":0,"y":0.25,"w":0.5,"h":0.5,"type":0,"status":1,"muted":0,"vol":1,"vad":119},{"uid":"viewer222","paneid":1,"zorder":1,"x":0.5018382,"y":0.25,"w":0.5,"h":0.5,"type":0,"status":1,"muted":0,"vol":60,"vad":123}],"ver":"1.0.0.20220915","ts":1697696106230} By checking the number of elements in the `stream` array, you can determine whether the live layout has changed. If the `stream` array has one element, a single streamer is ingesting a stream. If the `stream` array has more than one element, the streamer is in a co-streaming or PK session. The layout information for each member indicates their specific position in the mixed stream layout.

Pass-through SEI

• To use custom SEI, you can call the StartLiveMPUTask command to start a stream mixing and ingest task and specify `PayloadContent` in the `PassThrough` parameter. You can also call the UpdateLiveMPUTask command to update the task and specify `PayloadContent` in the `PassThrough` parameter.

• Custom SEI can be sent periodically. You can set the period using the `Interval` parameter in `PassThrough`. The unit is milliseconds.

• Custom SEI can also be sent with keyframes. You can set this using the `FollowIdr` parameter in `PassThrough`.

  • You can send SEI both periodically and with keyframes. For example, `Interval:1000` and `FollowIdr: 1` means that custom SEI is sent every 1000 ms and also with every keyframe.

  • If you do not set `Interval` or `FollowIdr`, the custom SEI is sent only once when the API is called.

For example, when streamer `streamer111` is streaming alone, you can call the UpdateLiveMPUTask command to send periodic SEI. In the `PassThrough` parameter, set `Interval` to 1000, `FollowIdr` to 0, and `PayloadContent` to "hello world". A custom SEI message is then sent every 1000 ms. The SEI frame format that the viewer receives is as follows:
{"canvas":{"w":1920,"h":1080,"bgnd":0},"stream":[{"uid":"streamer111","paneid":-1,"zorder":0,"x":0,"y":0,"w":0,"h":0,"type":0,"status":1,"muted":0,"vol":0,"vad":0}],"ver":"1.0.0.20220915","ts":1697696109876,"udd":"hello world"}

Cross-channel multi-user stream mixing

To mix streams from multiple streamers across multiple channels and ingest the mixed stream to the live streaming service, you must provide the UserID and ChannelID of the streamer who initiates the cross-channel call, along with the UserIDs of the other participants, as input parameters when you create the stream mixing task. See the following example: In a live PK scenario, streamer `userA` in channel `channelA` initiates a cross-channel PK with streamer `userB` in channel `channelB` using a client API. The mixed stream of both streamers is output to the viewers in channel `channelA`. In this case, the channel and user parameters for creating the stream mixing task are specified as follows:

• ChannelID: Specify `channelA`.

• UserInfos->UserId: Specify `userA` and `userB` respectively.