aiortc: WebRTC and ORTC Implementation for Python

Warnings

• breaking The `RTCDataChannel.send` method has historically changed between being a regular function and a coroutine. While currently a coroutine, be aware of this breaking change if upgrading from older versions, particularly around 0.9.x.
  Fix: Ensure `await` is used when calling `RTCDataChannel.send()` if you are on a version where it's a coroutine. Review the changelog for specific version behavior.
• breaking Older Python versions are no longer supported. aiortc dropped support for Python 3.5 (0.9.23), 3.6 (1.3.0), and 3.8 (1.10.0).
  Fix: Ensure your environment uses Python 3.10 or newer to be compatible with the latest aiortc releases.
• gotcha When using `MediaRecorder` with `PyAV` for video, the default resolution can be hardcoded to 640x480, and `aiortc` might not automatically adjust it. This can lead to unexpected video sizes if not explicitly handled.
  Fix: Explicitly configure the video size when initializing `MediaPlayer` or `MediaRecorder` if a different resolution is desired.
• gotcha For outgoing media tracks, it is crucial to establish and add the track to the `RTCPeerConnection` *before* the server sends back the ICE response during the signaling process. Failing to do so can result in the peer connection opening in a 'recvonly' mode, preventing the sending of media.
  Fix: Ensure your signaling logic properly synchronizes the addition of outgoing tracks with the exchange of ICE candidates and SDP answers.
• gotcha The `MediaRecorder` consumes incoming tracks and does not natively manage presentation timestamp (PTS) gaps caused by network interruptions. Directly recording an incoming track with `MediaRecorder` can lead to reception halting if there are PTS discontinuities.
  Fix: For scenarios requiring robust recording of incoming tracks while also re-transmitting them, use a `MediaRelay` to duplicate the track and feed one stream to the `MediaRecorder` and the other to the outgoing peer connection. Implement custom logic to handle PTS adjustments if direct recording of lossy streams is necessary.

Install

• pip install aiortc Base installation
• pip install aiohttp aiortc opencv-python With common dependencies for server examples

Imports

• RTCPeerConnection

  from aiortc import RTCPeerConnection

• RTCSessionDescription

  from aiortc import RTCSessionDescription

• RTCConfiguration

  from aiortc import RTCConfiguration

• MediaStreamTrack

  from aiortc.mediastreams import MediaStreamTrack

• VideoStreamTrack

  from aiortc.mediastreams import VideoStreamTrack

• AudioStreamTrack

  from aiortc.mediastreams import AudioStreamTrack

• RTCDataChannel

  from aiortc import RTCDataChannel

• RTCCertificate

  from aiortc import RTCCertificate

• generateCertificate

  from aiortc import RTCCertificate, generateCertificate

  A class method of RTCCertificate, often imported alongside it.
• MediaRelay

  from aiortc.contrib.media import MediaRelay

  MediaRelay is in the 'contrib.media' submodule, not directly under 'aiortc'.
• MediaPlayer

  from aiortc.contrib.media import MediaPlayer

  MediaPlayer is in the 'contrib.media' submodule, not directly under 'aiortc'.

Quickstart

This quickstart demonstrates the basic setup of an `RTCPeerConnection` and the generation of an SDP offer. In a full WebRTC application, this offer would be exchanged with a remote peer via a signaling server, and an answer would be received and set as the remote description. The example includes placeholders for a simulated answer and a loop to keep the connection alive. It highlights the core `RTCPeerConnection` object and its `createOffer` and `setLocalDescription` methods. For practical examples with media and data channels, refer to the `aiortc` examples directory on GitHub, especially the `server` example.

import asyncio
from aiortc import RTCPeerConnection, RTCSessionDescription

async def main():
    pc = RTCPeerConnection()
    print("RTCPeerConnection created.")

    # Example: Create an offer (typically this is exchanged via a signaling server)
    offer = await pc.createOffer()
    await pc.setLocalDescription(offer)
    print(f"Local SDP Offer:\n{pc.localDescription.sdp}")

    # In a real application, you'd send pc.localDescription to a remote peer
    # and receive their answer, then set it as remoteDescription.
    # For this quickstart, we'll simulate a minimal answer (not fully functional for media).

    # Simulate receiving an answer (replace with actual signaling in a real app)
    # For a real peer, this would be generated by the remote peer's createAnswer()
    # and contain media tracks if applicable.
    # remote_sdp_answer = "v=0\r\no=- 12345 12345 IN IP4 127.0.0.1\r\ns=-\r\nt=0 0\r\na=fingerprint:sha-256 A0:B1:C2:D3:E4:F5:G6:H7:I8:J9:K0:L1:M2:N3:O4:P5:Q6:R7:S8:T9:U0:V1:W2:X3:Y4\r\na=group:BUNDLE audio video\r\na=msid-semantic:WMS\r\nm=audio 9 UDP/TLS/RTP/SAVPF 111\r\na=rtcp-mux\r\na=rtpmap:111 OPUS/48000/2\r\na=mid:audio\r\nm=video 9 UDP/TLS/RTP/SAVPF 96\r\na=rtcp-mux\r\na=rtpmap:96 VP8/90000\r\na=mid:video\r\n"
    # remote_description = RTCSessionDescription(sdp=remote_sdp_answer, type="answer")
    # await pc.setRemoteDescription(remote_description)
    # print("Remote SDP Answer set (simulated).")

    # Keep the connection alive for a short period or until closed by events
    try:
        while pc.connectionState != "closed" and pc.connectionState != "failed":
            await asyncio.sleep(1)
    except asyncio.CancelledError:
        pass
    finally:
        print("Closing peer connection...")
        await pc.close()
        print("Peer connection closed.")

if __name__ == "__main__":
    # Ensure auth check passes for quickstart (not applicable for aiortc directly)
    # For real use cases, replace os.environ.get with actual credentials if needed by signaling.
    # Example: if you had a signaling server requiring a token:
    # import os
    # if not os.environ.get('WEBRTC_AUTH_TOKEN'):
    #     print("Warning: WEBRTC_AUTH_TOKEN not set. Quickstart might fail in a real scenario.")
    asyncio.run(main())