av.open(timeout) is capped at 20 seconds

[Pnaop]

Overview

I am using an SDP file to stream RTP to pyav. I get the frames in a thread.

The timeout argument for av.open() seems to be capped at around 20 seconds. I need to be able to wait for a period longer than 20 seconds, but the container always times out.

EDIT: While writing this bug report, I did find a possible fix by using the FFmpeg arg listen_timeout.

Expected behavior

I would expect the open en read timeout to be configurable above 20s using the specified (float) values.

Actual behavior

When no stream is available, av.open times out after 20s when a higher time is specified.

Traceback:

Exception in thread Thread-1 (get_frame):
Traceback (most recent call last):
  File "threading.py", line 1016, in _bootstrap_inner
  File "threading.py", line 953, in run
  File "pyav_get_frames.py", line 71, in get_frame
  File "av\container\input.pyx", line 202, in decode
  File "av\container\input.pyx", line 162, in demux
  File "av\container\core.pyx", line 292, in av.container.core.Container.err_check
  File "av\error.pyx", line 336, in av.error.err_check
av.error.UndefinedError: [Errno 138] Error number -138 occurred: 'C:\\dir\\rtpstream.sdp'; last error log: [h264] error while decoding MB 79 36

Investigation

I've tried a selection of values, 3, 5 and 10 all work as expected.
When using a value above 20 (30, 60, etc.), the timeout is still at around 20 seconds.

I have tried to specify the timeout with the ffmpeg args as well: options={"protocol_whitelist": "file,udp,rtp", "timeout":"30000"}

I found that the default value is 20, which I can indeed confirm.

Possible cause/fix:
After reading the commit diff, I tried to use listen_timeout;

# Open the RTP stream.
self.input_video = av.open(sdp_path, options={"protocol_whitelist": "file,udp,rtp", "listen_timeout": "30000"})

And that did work! Note, this is value is probably in seconds for RTP...

Reproduction

rtpstream.sdp:

v=0
c=IN IP4 127.0.0.1
m=video 5000 RTP/AVP 96
a=rtpmap:96 H264/90000

pyav_get_frames.py:

import av
from collections import deque
from threading import Thread

class GetFrames:
    def __init__(self):
        # Setup thread to read frames from the video stream.
        self.thread = None
        self.input_video = None
        self.deque = deque(maxlen=2)

    def start_streaming(self, sdp_path):
        # Open the RTP stream.
        self.input_video = av.open(sdp_path, options={"protocol_whitelist": "file,udp,rtp"}, timeout=30.0)

        stream = self.input_video.streams.video[0]
        stream.codec_context.skip_frame = "NONKEY"

        # Get one frame to initialize the buffer.
        self.get_frame(once=True)

        # Setup thread to read frames from the video stream.
        self.thread = Thread(target=self.get_frame, args=(), daemon=True)
        self.thread.start()
   
    def get_frame(self, once=False):
        for frame in self.input_video.decode():
            self.deque.append(frame)  # Circular buffer
            if once:
                return

I handle the frames in the buffer elsewhere.

Versions

• OS: Windows 10 22H2
• PyAV runtime:

PyAV v10.0.0
library configuration: --disable-static --enable-shared --libdir=/c/cibw/vendor/lib --prefix=/c/cibw/vendor --disable-alsa --disable-doc --disable-mediafoundation --enable-fontconfig --enable-gmp --disable-gnutls --enable-gpl --enable-libaom --enable-libass --enable-libbluray --enable-libdav1d --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --disable-libxcb --enable-libxml2 --enable-libxvid --enable-lzma --enable-version3 --enable-zlib
library license: GPL version 3 or later
libavcodec     59. 37.100
libavdevice    59.  7.100
libavfilter     8. 44.100
libavformat    59. 27.100
libavutil      57. 28.100
libswresample   4.  7.100
libswscale      6.  7.100

• FFmpeg:

ffmpeg version N-109165-g9f5a9a7499-20221122 Copyright (c) 2000-2022 the FFmpeg developers
built with gcc 12.2.0 (crosstool-NG 1.25.0.90_cf9beb1)
configuration: --prefix=/ffbuild/prefix --pkg-config-flags=--static --pkg-config=pkg-config --cross-prefix=x86_64-w64-mingw32- --arch=x86_64 --target-os=mingw32 --enable-version3 --disable-debug --disable-w32threads --enable-pthreads --enable-iconv --enable-libxml2 --enable-zlib --enable-libfreetype --enable-libfribidi --enable-gmp --enable-lzma --enable-fontconfig --enable-libvorbis --enable-opencl --disable-libpulse --enable-libvmaf --disable-libxcb --disable-xlib --enable-amf --enable-libaom --enable-libaribb24 --disable-avisynth --enable-chromaprint --enable-libdav1d --disable-libdavs2 --disable-libfdk-aac --enable-ffnvcodec --enable-cuda-llvm --disable-frei0r --enable-libgme --enable-libkvazaar --enable-libass --enable-libbluray --enable-libjxl --enable-libmp3lame --enable-libopus --enable-librist --enable-libssh --enable-libtheora --enable-libvpx --enable-libwebp --enable-lv2 --disable-libmfx --enable-libvpl --enable-openal --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg --enable-libopenmpt --enable-librav1e --disable-librubberband --enable-schannel --enable-sdl2 --enable-libsoxr --enable-libsrt --enable-libsvtav1 --enable-libtwolame --enable-libuavs3d --disable-libdrm --disable-vaapi --disable-libvidstab --enable-vulkan --enable-libshaderc --enable-libplacebo --disable-libx264 --disable-libx265 --disable-libxavs2 --disable-libxvid --enable-libzimg --enable-libzvbi --extra-cflags=-DLIBTWOLAME_STATIC --extra-cxxflags= --extra-ldflags=-pthread --extra-ldexeflags= --extra-libs=-lgomp --extra-version=20221122
libavutil      57. 43.100 / 57. 43.100
libavcodec     59. 54.100 / 59. 54.100
libavformat    59. 34.101 / 59. 34.101
libavdevice    59.  8.101 / 59.  8.101
libavfilter     8. 50.101 /  8. 50.101
libswscale      6.  8.112 /  6.  8.112
libswresample   4.  9.100 /  4.  9.100

Research

I have done the following:

• Checked the PyAV documentation
• Searched on Google
• Searched on Stack Overflow
• Looked through old GitHub issues
• Asked on PyAV Gitter
• ... and waited 72 hours for a response.

Additional context