Chrome Android 未使用 SDP 提供的所有编解码器选项

Question

When I run RTCRtpSender.getCapabilities("video").codecs; on Chrome Android it includes H264. However, I run var offer = RTCPeerConnection.createOffer() and look at offer.sdp it will only sometimes include H264 in the offer. This is causing me issues with an application that requires H264 - it works inconsistently as a result of rejecting those offers that don't include H264, and I don't know how to force the SDP offer to include it. How do I make sure createOffer includes all available codecs? I would prefer not to have to do any manual editing of the SDP.

Answer 1

I've been facing the same problem. As Pedro Vergara commented, it looks like a bug introduced in recent versions of Chrome Android. For now, I did a simple workaround by keep calling RTCRtpSender.getCapabilities('video') until it lists the expected H.264 codec support, before any attempt to create the SDP offer. Something like this:

console.log('Waiting for H.264 codec support');
checkH264(20);

function checkH264(count) {
  if (count > 0) {
    console.log('Getting video codec capabilities');
    let capabilities = JSON.stringify(RTCRtpSender.getCapabilities('video').codecs);
    console.log(capabilities);
    if (capabilities.toLowerCase().includes('video/h264')) {
      console.log('H.264 support found. Ready to proceed now! =)');
      // Proceed to SDP offer creation...
    } else {
      setTimeout(checkH264, 1000, count - 1);
    }
  } else {
    console.warn('H.264 support not found');
    // Proceed with caution. SDP offer may not contain H.264...
  }
}

Notice that the code above gives some time for Chrome to make H.264 available, by using setTimeout() . Just calling RTCRtpSender.getCapabilities('video') twice or more without really waiting may not work.