Capture frame failed

[vuleetu]

I found a lot ofRtcError errors in worker logs.

Nov 28 01:57:50 python[117393]:     await self._audio_source.capture_frame(frame)
Nov 28 01:57:50 python[117393]:   File "/home/ubuntu/miniconda3/envs/chat/lib/python3.12/site-packages/livekit/rtc/audio_source.py", line 152, in capture_frame
Nov 28 01:57:50 python[117393]:     raise Exception(cb.capture_audio_frame.error)
Nov 28 01:57:50 python[117393]: Exception: an RtcError occured: InvalidState - failed to capture frame {"pid": 121680, "job_id": "AJ_oHY4vMyQc8kr"}

Transcriptions were streamed to client normally, but TTS were lost. I need help to figure out how to avoid this issue

[btakita]

I'm also getting this error when streaming audio after the room opens. Is there any chance that the error message can provide more detail in what state is invalid?

[boyko11]

After I dug down to the Rust code: https://github.com/livekit/rust-sdks/blob/0773bcec4e24812b382e71166b2ab359bf1a9384/libwebrtc/src/native/audio_source.rs#L87

and with some LLM help, I was able to alleviate the issue in our python code by doubling the size of the queue_size_ms:

audio_source = rtc.AudioSource(
            sample_rate=<our_sample_rate>,
            num_channels=<our_num_channels>,
            queue_size_ms=2000

I was able to reproduce it fairly consistently by setting the queue_size_ms to min allowed value of 10

[vishnukool]

I am facing the exact same issue. TTS is lost but text transmission continues. Why is this marked as Not planned?

[ladvoc]

I think this was closed automatically due to inactivity, but I’ll reopen it since it appears that this issue persists.

[ladvoc]

@vishnukool, would you mind sharing what version of the agents framework you are using?

[vishnukool]

Yes, it's happening unfortunately and really annoying since on long stories voice just stops. We use below

livekit-agents[google,anthropic,silero,turn-detector,openai,cartesia,deepgram,elevenlabs]~=1.0.23

ANd below is the error log

{"message": "Error in _audio_forwarding_task\nTraceback (most recent call last):\n  File \"/home/appuser/.local/lib/python3.11/site-packages/livekit/agents/voice/generation.py\", line 237, in _audio_forwarding_task\n    await audio_output.capture_frame(f)\n  File \"/home/appuser/.local/lib/python3.11/site-packages/livekit/agents/voice/transcription/synchronizer.py\", line 487, in capture_frame\n    await self._next_in_chain.capture_frame(frame)  # passthrough audio\n    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n  File \"/home/appuser/.local/lib/python3.11/site-packages/livekit/agents/voice/room_io/_output.py\", line 78, in capture_frame\n    await self._audio_source.capture_frame(frame)\n  File \"/home/appuser/.local/lib/python3.11/site-packages/livekit/rtc/audio_source.py\", line 142, in capture_frame\n    cb: proto_ffi.FfiEvent = await queue.wait_for(\n                             ^^^^^^^^^^^^^^^^^^^^^\n  File \"/home/appuser/.local/lib/python3.11/site-packages/livekit/rtc/_utils.py\", line 81, in wait_for\n    event = await self.get()\n            ^^^^^^^^^^^^^^^^\n  File \"/usr/local/lib/python3.11/asyncio/queues.py\", line 158, in get\n    await getter\nasyncio.exceptions.CancelledError\n\nDuring handling of the above exception, another exception occurred:\n\nTraceback (most recent call last):\n  File \"/home/appuser/.local/lib/python3.11/site-packages/livekit/agents/utils/log.py\", line 16, in async_fn_logs\n    return await fn(*args, **kwargs)\n           ^^^^^^^^^^^^^^^^^^^^^^^^^\n  File \"/home/appuser/.local/lib/python3.11/site-packages/livekit/agents/voice/generation.py\", line 251, in _audio_forwarding_task\n    await audio_output.capture_frame(frame)\n  File \"/home/appuser/.local/lib/python3.11/site-packages/livekit/agents/voice/transcription/synchronizer.py\", line 487, in capture_frame\n    await self._next_in_chain.capture_frame(frame)  # passthrough audio\n    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n  File \"/home/appuser/.local/lib/python3.11/site-packages/livekit/agents/voice/room_io/_output.py\", line 78, in capture_frame\n    await self._audio_source.capture_frame(frame)\n  File \"/home/appuser/.local/lib/python3.11/site-packages/livekit/rtc/audio_source.py\", line 149, in capture_frame\n    raise Exception(cb.capture_audio_frame.error)\nException: an RtcError occured: InvalidState - failed to capture frame", "level": "ERROR", "name": "livekit.agents", "pid": 213, "job_id": "AJ_UtLmTe5439Hx", "timestamp": "2025-10-22T19:09:32.832086+00:00"}

[vishnukool]

OK returning the favor to the world. This got fixed by updating livekit agents to latest - livekit-agents 1.2.15

[ladvoc]

That's good to hear, thank you for confirming!