Get Discrete audio from a Teams meeting with the Calling SDK

Question

Get Discrete audio from a Teams meeting with the Calling SDK

Skype Bonding 0

Hi,

Is it possible to get discrete audio from a Teams meeting with the calling SDK?

I can get the mixed audio but I'm not sure if it's possible to get the individual audio for each person in the meeting.

Thanks

Simon

Jerald Felix 2,180

Hello,

Yes — the Azure Communication Services (ACS) Calling SDK does let you pull each participant’s audio as a separate stream, you just have to subscribe to the right objects.

1 How the SDK exposes “un-mixed” audio

Every remote user that joins the call surfaces as a RemoteParticipant.

Each RemoteParticipant owns one or more RemoteAudioStream objects.

The SDK raises remoteAudioStreamsUpdated whenever streams are added or removed; that is your cue to start or stop processing that person’s audio.

“For incoming remote unmixed audio the client Calling SDK will have access to the individual audio streams of each participant on the call.”

call.remoteParticipants.forEach(p => {
  // existing participants
  wireParticipant(p);
});

call.on('remoteParticipantsUpdated', e => {
  e.added.forEach(wireParticipant);
});

function wireParticipant(participant) {
  participant.remoteAudioStreams.forEach(stream => handleStream(participant.identifier, stream));

  participant.on('remoteAudioStreamsUpdated', ev => {
    ev.added.forEach(stream  => handleStream(participant.identifier, stream));
    ev.removed.forEach(stopProcessing);
  });
}

handleStream is where you hand the raw PCM to a WebAudio node, Speech-to-Text engine, file sink, and so on.

2 Things to keep in mind

Limitation	Details
Max 4 live channels	Only the four most dominant speakers are delivered concurrently; when a new speaker becomes dominant the least-recent one is swapped out. (Microsoft Learn)
Max 4 live channels	Only the four most dominant speakers are delivered concurrently; when a new speaker becomes dominant the least-recent one is swapped out.
Teams interop	The same API works when you join a Teams meeting through ACS, but the 4-channel rule still applies.
Browser output	The SDK exposes the raw `MediaStreamTrack`; if you want to play the audio locally you still need to hook it to an `HTMLAudioElement` or WebAudio graph.
Recording vs. real-time	If you don’t need the audio in real-time, start an unmixed recording instead (`recordingChannelType: "unmixed"`). The service will store a WAV/MP4 file where each participant sits on its own channel.
Server-side streaming (preview)	Need per-speaker audio on the server for live AI? Call Automation’s bidirectional audio streaming can push the same unmixed channels over WebSocket, ready for Azure OpenAI or STT.

3 Troubleshooting checklist

Verified event wiring? Make sure you’re handling both existing remoteParticipants at join time and any that arrive later.
Correct SDK version? Unmixed audio landed in Calling SDK 1.15 (JS) / 2.4 (Android) / 2.3 (iOS) or later.
Teams meeting >100 participants? After the 100-participant mark only the video feeds of the dominant 4 are sent, but audio behaviour stays the same; still only four audio tracks at once.
Low-latency processing? Use Worklets or the AudioContext “processor” node rather than ScriptProcessor (deprecated) to keep latency down.

Just subscribe to every RemoteParticipant.remoteAudioStreams and you’ll have one PCM stream per speaker in real time. If you hit the four-channel ceiling or need a post-call artefact, switch to unmixed recording or to the new Call Automation audio-streaming preview.Yes — the Azure Communication Services (ACS) Calling SDK does let you pull each participant’s audio as a separate stream, you just have to subscribe to the right objects.

Best Regards,

Jerald Felix

Laxman Reddy Revuri 5,405 Reputation points Microsoft External Staff Moderator

2025-06-03T03:57:19.41+00:00

Hi Skype Bonding,
Just checking in to see if above information was helpful. If you have any further updates on this issue, please feel free to post back.
Thank you for answering @Jerald Felix
Skype Bonding 0 Reputation points

2025-06-03T08:21:18.8233333+00:00

Hi,

Thanks for the quick response.

Do you know if this is available in the c# sdk as well as the js?

Thanks

Simon
Jerald Felix 2,180 Reputation points

2025-06-03T09:46:00.4466667+00:00
Hello Simon,

Yes, it is possible to obtain discrete (unmixed) audio streams for each participant in a Microsoft Teams meeting using the Azure Communication Services (ACS) Calling SDK. This capability allows you to access individual audio streams in real-time.

How to Access Discrete Audio Streams

Each participant in a call is represented as a RemoteParticipant object. These participants have associated remoteAudioStreams that you can subscribe to. The SDK provides events to notify you when audio streams are added or removed, enabling you to handle each participant’s audio individually.

Here’s a simplified example in JavaScript:

call.remoteParticipants.forEach(participant => {

wireParticipant(participant);

});

call.on('remoteParticipantsUpdated', event => {

event.added.forEach(wireParticipant);

});

function wireParticipant(participant) {

participant.remoteAudioStreams.forEach(stream => handleStream(participant.identifier, stream));

participant.on('remoteAudioStreamsUpdated', ev => {

ev.added.forEach(stream => handleStream(participant.identifier, stream));

ev.removed.forEach(stopProcessing);

});

}

In this example, handleStream is a function where you process the raw PCM audio data, which can be directed to a WebAudio node, a speech-to-text engine, a file sink, or other processing units.

Limitations to Consider

Maximum of 4 Live Channels: The SDK delivers audio streams for up to four dominant speakers concurrently. When a new participant becomes dominant, the least recent one is swapped out.

Teams Interoperability: This functionality is also available when joining a Teams meeting through ACS. However, the four-channel limitation still applies.

Browser Output: The SDK exposes raw MediaStreamTrack objects. To play the audio locally, you need to connect these tracks to an HTMLAudioElement or a WebAudio graph.

Recording vs. Real-Time: If real-time processing isn’t required, you can initiate an unmixed recording by setting recordingChannelType: "unmixed". This will store each participant’s audio on separate channels in a WAV/MP4 file.

Server-Side Streaming (Preview): For server-side processing, such as live AI applications, the Call Automation’s bidirectional audio streaming can push unmixed channels over WebSocket, suitable for integration with Azure OpenAI or speech-to-text services.

Troubleshooting Tips

Event Handling: Ensure you’re subscribing to both existing remoteParticipants at the time of joining and any new participants that join later.

SDK Version: Unmixed audio support was introduced in Calling SDK versions 1.15 (JavaScript), 2.4 (Android), and 2.3 (iOS). Make sure you’re using an appropriate version.

Large Meetings: In meetings with more than 100 participants, only the video feeds of the dominant four are sent. However, the audio behavior remains the same, with only four audio tracks available concurrently.

Low-Latency Processing: To minimize latency, use Audio Worklets or the AudioContext’s processor node instead of the deprecated ScriptProcessor.

By subscribing to each RemoteParticipant.remoteAudioStreams, you can obtain one PCM stream per speaker in real-time. If you encounter the four-channel limitation or require post-call artifacts, consider using unmixed recordings or the new Call Automation audio-streaming preview.

Best Regards,

Jerald Felix
Skype Bonding 0 Reputation points

2025-06-03T11:04:57.6233333+00:00

Hi, That looks like it's the javascript again.

It looks like the c# sdk only has the mixed audio for a teams meeting as far as I can see.

Thanks

Simon

1 answer

Your answer

Laxman Reddy Revuri 5,405 Reputation points Microsoft External Staff Moderator

2025-06-03T03:57:19.41+00:00

Hi Skype Bonding,
Just checking in to see if above information was helpful. If you have any further updates on this issue, please feel free to post back.
Thank you for answering @Jerald Felix
Skype Bonding 0 Reputation points

2025-06-03T08:21:18.8233333+00:00

Hi,

Thanks for the quick response.

Do you know if this is available in the c# sdk as well as the js?

Thanks

Simon
Skype Bonding 0 Reputation points

2025-06-03T11:04:57.6233333+00:00

Hi, That looks like it's the javascript again.

It looks like the c# sdk only has the mixed audio for a teams meeting as far as I can see.

Thanks

Simon

Answer 1

Laxman Reddy Revuri 5,405 Microsoft External Staff Moderator

Hi Skype Bonding,
Unfortunately, as you mentioned, obtaining discrete audio streams may not be available in the C# SDK at this time, as it primarily supports mixed audio for Teams meetings.

Please accept as "Yes" if the answer provided is useful, so that you can help others in the community looking for remediation for similar issues.

Laxman Reddy Revuri 5,405 Reputation points Microsoft External Staff Moderator

2025-06-05T04:07:47.56+00:00

Hi Skype Bonding,
If the answer is helpful, please click Accept Answer and kindly upvote it so that other people who faces similar issue may get benefitted from it.
Laxman Reddy Revuri 5,405 Reputation points Microsoft External Staff Moderator

2025-06-09T01:06:08.7733333+00:00

Hi Skype Bonding,
If the answer is helpful, please click Accept Answer and kindly upvote it so that other people who faces similar issue may get benefitted from it.

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Get Discrete audio from a Teams meeting with the Calling SDK

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