WebRTC: Support stereo in SDP answer for players

[superyhee]

Note: Please read FAQ before file an issue, see #2716

Description

Please description your issue here

1. SRS Version: v5.0-a4
2. SRS Log:

xxxxxxxxxxxx
xxxxxxxxxxxx
xxxxxxxxxxxx

3. SRS Config:

   rtc {
   enabled on;
   # @see https://github.com/ossrs/srs/wiki/v4_CN_WebRTC#rtmp-to-rtc
   rtmp_to_rtc on;
   # @see https://github.com/ossrs/srs/wiki/v4_CN_WebRTC#rtc-to-rtmp
   rtc_to_rtmp on;
   keep_bframe off;
   }
   `

Expect

Use music file streaming through RTC, use RTC or RTC2RTMP for pulling streams. The audio is not in stereo, so you need to add stereo=1 in the a=ftmp line of the SDP to represent dual-channel, and stereo=0 represents mono-channel.
a=fmtp:111 minptime=10;useinbandfec=1; stereo=1; maxaveragebitrate=192000
I used the following method on the client-side.
async function run() { const offer = await peerConnection.createOffer();
offer.sdp = offer.sdp.replace('useinbandfec=1', 'useinbandfec=1; stereo=1; sprop-stereo=1;stereo=1; maxaveragebitrate=192000')
await peerConnection.setLocalDescription(offer)
Can the server-side support stereo=1 through configuration?

TRANS_BY_GPT3

[winlinvip]

This is a feature, please update your issue and describe more details about the backgroud and use scenarios, or we will delete it.

[superyhee]

The main use case is to use RTC to implement web live streaming, which requires playing high-quality music during the live stream, such as playing stereo music. Currently, SRS using RTC or RTC2RTMP does not support stereo sound.

TRANS_BY_GPT3