Voice and video calls

gotd implements Telegram's tgcalls over WebRTC in the calls package, supporting both 1:1 calls and group voice chats. This is an advanced feature that builds on the rest of the library — authenticate and handle updates first.

Audio pipeline

The examples transcode MP3 to Opus with ffmpeg and feed the resulting RTP packets into the call. You need ffmpeg available, and you bring your own audio source. The helper examples.StreamMP3(ctx, writePacket, path) encapsulates the transcoding.

1:1 calls

Create a call client, register it on your dispatcher so it sees signaling updates, then place a call to a user:

import "github.com/gotd/td/telegram/calls"

callClient := calls.NewClient(api, calls.Options{Logger: logzap.New(log)})
callClient.Register(dispatcher)

conn, err := callClient.Request(ctx, user) // user is a tg.InputUserClass
if err != nil {
	return err
}
defer callClient.Discard(ctx, calls.DiscardHangup)

connected := make(chan struct{})
conn.OnConnected(func() { close(connected) })
<-connected

// Stream audio into the call's RTP track.
if err := examples.StreamMP3(ctx, conn.AudioTrack().WriteRTP, audioPath); err != nil {
	return err
}

conn.AudioTrack() is a webrtc.TrackLocalStaticRTP you write packets to. This is the call example.

Group voice chats

Join a supergroup or channel's voice chat with a GroupCall:

gc := calls.NewGroupCall(client.API(), calls.Options{Logger: logzap.New(log)})
gc.Register(dispatcher)
gc.OnParticipants(func(p []tg.GroupCallParticipant) {
	log.Info("participants", zap.Int("count", len(p)))
})

joinAs := &tg.InputPeerUser{UserID: self.ID, AccessHash: self.AccessHash}
if err := gc.Join(ctx, call, joinAs); err != nil { // call is a *tg.InputGroupCall
	return err
}
defer gc.Leave(ctx)

if err := examples.StreamMP3(ctx, gc.WriteAudio, audioPath); err != nil {
	return err
}

gc.WriteAudio(pkt *rtp.Packet) feeds audio into the group call. This is the groupcall example.

Caveats

• Calls require a user session (QR or code login), not a bot.
• You must obtain the *tg.InputGroupCall for a chat before joining (resolve the chat, then read its full info).
• Video is supported by the underlying protocol, but the examples stream audio only.
• This is one of the more involved parts of the library — read the example sources in full before building on them.