aiortc and Alexa.RTCSessionControllerInterface

I’m trying to use aiortc to serve video to Amazon Alexa’s RTCSessionControllerInferface (https://developer.amazon.com/en-US/docs/alexa/device-apis/alexa-rtcsessioncontroller.html)

The SDP I receive is this:

v=0
o=- 3824376089 3824376089 IN IP4 0.0.0.0
s=a 2 z
c=IN IP4 0.0.0.0
t=0 0
a=group:BUNDLE audio0 video0
m=audio 1 UDP/TLS/RTP/SAVPF 96 0
a=candidate:1 1 UDP 2013266431 3.250.43.172 50101 typ host
a=candidate:2 1 TCP 1015021823 3.250.43.172 9 typ host tcptype active
a=candidate:1 2 UDP 2013266430 3.250.43.172 56409 typ host
a=candidate:2 2 TCP 1015021822 3.250.43.172 9 typ host tcptype active
a=candidate:3 1 TCP 1010827519 3.250.43.172 46500 typ host tcptype passive
a=candidate:3 2 TCP 1010827518 3.250.43.172 48985 typ host tcptype passive
a=setup:actpass
a=extmap:3 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time
a=rtpmap:96 opus/48000/2
a=rtcp:9 IN IP4 0.0.0.0
a=rtcp-mux
a=sendrecv
a=mid:audio0
a=ssrc:3458962346 cname:user3441999428@host-c15765d
a=ice-ufrag:/yto
a=ice-pwd:AuahTawelYzLoadB5TAg7/
a=fingerprint:sha-256 8F:7B:D2:29:93:75:EA:18:81:56:9A:78:9C:F3:B3:67:C6:2F:25:0D:67:13:AA:5C:FF:38:39:22:04:70:C8:06
m=video 1 UDP/TLS/RTP/SAVPF 99
a=candidate:1 1 UDP 2013266431 3.250.43.172 50101 typ host
a=candidate:3 1 TCP 1010827519 3.250.43.172 46500 typ host tcptype passive
a=candidate:2 1 TCP 1015021823 3.250.43.172 9 typ host tcptype active
a=candidate:3 2 TCP 1010827518 3.250.43.172 48985 typ host tcptype passive
a=candidate:1 2 UDP 2013266430 3.250.43.172 56409 typ host
a=candidate:2 2 TCP 1015021822 3.250.43.172 9 typ host tcptype active
b=AS:2500
a=setup:actpass
a=extmap:3 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time
a=rtpmap:99 H264/90000
a=rtcp:9 IN IP4 0.0.0.0
a=rtcp-mux
a=sendrecv
a=mid:video0
a=rtcp-fb:99 nack
a=rtcp-fb:99 nack pli
a=rtcp-fb:99 ccm fir
a=ssrc:4150294130 cname:user3999939428@host-c12365d
a=ice-ufrag:/yto
a=ice-pwd:AtyuTPJqlYzLoadB5TAg7/
a=fingerprint:sha-256 8F:7B:D2:29:93:75:EA:18:81:56:9A:78:9C:F3:B3:67:C6:2F:25:0D:67:13:AA:5C:FF:38:39:22:04:70:C8:06

when I try to send back an rtsp stream I get back:

ERROR:aiohttp.server:Error handling request
Traceback (most recent call last):
  File "/home/x/github/core/venv/lib/python3.8/site-packages/aiohttp/web_protocol.py", line 422, in _handle_request
    resp = await self._request_handler(request)
  File "/home/x/github/core/venv/lib/python3.8/site-packages/aiohttp/web_app.py", line 499, in _handle
    resp = await handler(request)
  File "server.py", line 63, in smart_home
    await pc.setRemoteDescription(offer)
  File "/home/x/github/core/venv/lib/python3.8/site-packages/aiortc/rtcpeerconnection.py", line 823, in setRemoteDescription
    assert len(common)
AssertionError

My code is :

async def smart_home(request):
    pc = RTCPeerConnection()

    audio, video = create_local_tracks(args.play_from)
    await pc.setRemoteDescription(offer)
    for t in pc.getTransceivers():
        if t.kind == "audio" and audio:
            pc.addTrack(audio)
        elif t.kind == "video" and video:
            pc.addTrack(video)

    answer = await pc.createAnswer()
    await pc.setLocalDescription(answer)

def create_local_tracks(play_from):
    global relay, webcam
    player = MediaPlayer("rtsp://web_cam_url")
    return player.audio, player.video

[jlaine]

I had a look at this and I think that in the absence of a profile, we should consider the remote party’s codec to be compatible so this looks like a bug indeed.

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