Recherche avancée

Sur d’autres sites (4406)

• Glitchy audio or broken video in fragmented MP4

  6 septembre 2022, par PookyFan

  I'm working on small C++ library for muxing audio and video. This is basically a facade for FFMPEG functions and structures. The code is here with minimal reproduction testing code here and as of now it seems like it's working fine... almost.

  


  For the record - my MP4 file is so-called "fragmented MP4", with headers moved at the beginning of the file in a way that would allow to stream that file (ie. play it in a browser while it's being buffered). That's what these movflags I'm setting in Mp4Muxer::writeHeader() are for.

  


  While testing this library with raw H264 video stream and MP3 file (video is <1 min long, MP3 - a few minutes long), I observed that :

  &#xA;

  &#xA;
  • if I don't limit muxing audio stream when it's way "ahead" of the video (and it will be since MP3 is longer, so eventually video frames stop coming but audio frames still come in), all muxes just fine with no errors, but playing output MP4 with ffplay after just a few seconds results in the following log (and also frozen video, while audio keeps playing) :

  &#xA;

  &#xA;

  [h264 @ 0x7f90a40ae2c0] Invalid NAL unit size (2162119 > 76779).0
[h264 @ 0x7f90a40ae2c0] Error splitting the input into NAL units.
[mp3float @ 0x7f90a4009540] Header missing  515KB sq=    0B f=0/0
[h264 @ 0x7f90a40cb0c0] Invalid NAL unit size (-860010620 > 17931).
[h264 @ 0x7f90a40cb0c0] Error splitting the input into NAL units.
[h264 @ 0x7f90a42bf440] Invalid NAL unit size (-168012642 > 8000).
[h264 @ 0x7f90a42bf440] Error splitting the input into NAL units.
[h264 @ 0x7f90a42fa780] Invalid NAL unit size (-1843711407 > 5683).
[ and it repeats...]


  &#xA;

  &#xA;
  • even if I limit how much a stream can be "ahead" of the other, limiting it too much results in no muxed data in the output

  &#xA;

  • any other intermediate level of limiting how much one stream can be buffered in muxer relative to the other stream results in glitchy audio, with the following errors popping out every now and then in ffplay (the more strict limit is, the more often they are printed) :

  &#xA;

  &#xA;

  [mp3float @ 0x7f744c01b640] overread, skip -6 enddists: -1 -1=0/0 


  &#xA;

  Not limitting muxed audio (at all or enough) relative to muxed video also results in following messages in my muxing application :

  &#xA;

  [mp4 @ 0x55d0c6c21940] Delay between the first packet and last packet in the muxing queue is 10004898 > 10000000: forcing output


  &#xA;

  For now, the fix is quite ugly and I don't even understand why it works, but before writting MP4 header I manually set a limit for frames buffered by muxer, like so :

  &#xA;

  formatCtxt->max_interleave_delta = 10000000LL * 10LL;


  &#xA;

  This way the muxer can store more packets of one stream that's way "ahead" of the other (maximum difference between DTS of the packets at the beginning and at the end of queue is set to 10x larger than default ; it also gets rid of information log mentioned above). Obviously, I'd like to resolve it more properly, without hacking things like that.

  &#xA;

  I was trying various things, including manual skipping of ID3 tags in MP3 file (but seems like FFMPEG handles them just fine and it didn't change anything). I was also experimenting with FLAC in MP4 instead of MP3. and while I know it's rather experimental thing, I encountered very similar problems with glitching audio (no problem with video being frozen when lots of audio data gets muxed, though). It also seems that problem with glitching audio or frozen video varies in scale depending on how large are input data chunks that I feed muxer with. For now, honestly, I'm out of ideas.

  &#xA;

• Non-monotonous DTS after 26:30:02.81 recording time

  24 mars, par micha

  I record an hls stream and after 26:30:02.81 there come the message :

  &#xA;&#xA;

  [http @ 0x558330f5ba80] Opening 'http://de-origin-live-be-01.3qsdn.com:8081/3279/996191_PwxkbnqRThCDGXVr/l_94_95438333_16449.ts?nimblesessionid=2106' for reading
frame=2289669 fps= 24 q=-1.0 size=25056768kB time=26:30:02.81 bitrate=2151.6kbits/s speed=   1x    
[mpegts @ 0x558330f07280] Invalid timestamps stream=0, pts=10378, dts=8589926250, size=11200
[mpegts @ 0x558330f07280] Invalid timestamps stream=0, pts=2908, dts=8589929940, size=3407
[mp4 @ 0x558330f20bc0] Non-monotonous DTS in output stream 0:0; previous: 8586744840, current: -3185972; changing to 8586744841. This may result in incorrect timestamps in the output file.
[mp4 @ 0x558330f20bc0] Non-monotonous DTS in output stream 0:1; previous: 4579598864, current: -1698561; changing to 4579598865. This may result in incorrect timestamps in the output file.
[mp4 @ 0x558330f20bc0] Non-monotonous DTS in output stream 0:1; previous: 4579598865, current: -1697537; changing to 4579598866. This may result in incorrect timestamps in the output file.
[mp4 @ 0x558330f20bc0] Non-monotonous DTS in output stream 0:1; previous: 4579598866, current: -1696513; changing to 4579598867. This may result in incorrect timestamps in the output file.
[mp4 @ 0x558330f20bc0] Non-monotonous DTS in output stream 0:0; previous: 8586744841, current: -3182282; changing to 8586744842. This may result in incorrect timestamps in the output file.
[mp4 @ 0x558330f20bc0] Non-monotonous DTS in output stream 0:1; previous: 4579598867, current: -1695489; changing to 4579598868. This may result in incorrect timestamps in the output file.
[mp4 @ 0x558330f20bc0] Non-monotonous DTS in output stream 0:1; previous: 4579598868, current: -1694465; changing to 4579598869. This may result in incorrect timestamps in the output file.
[mp4 @ 0x558330f20bc0] Non-monotonous DTS in output stream 0:1; previous: 4579598869, current: -1693441; changing to 4579598870. This may result in incorrect timestamps in the output file.
[mp4 @ 0x558330f20bc0] Non-monotonous DTS in output stream 0:0; previous: 8586744842, current: -3178502; changing to 8586744843. This may result in incorrect timestamps in the output file.
[mp4 @ 0x558330f20bc0] Non-monotonous DTS in output stream 0:0; previous: 8586744843, current: -3174722; changing to 8586744844. This may result in incorrect timestamps in the output file.


  &#xA;&#xA;

  There is no more video written to the file at this time but ffmpeg is not stopping. If i stop it manual after 30 hours the file is only 26 hours 30 minutes long.

  &#xA;&#xA;

  How to reproduce :

  &#xA;&#xA;

  ffmpeg -progress recorder.progress -reconnect 1 -user_agent 'sdn/1.0' -i http://source/playlist.m3u8 -codec copy -bsf:a aac_adtstoasc record.mp4

ffmpeg version 4.2.2 Copyright (c) 2000-2019 the FFmpeg developers
  built with gcc 7 (Ubuntu 7.4.0-1ubuntu1~18.04.1)
  configuration: --disable-debug --disable-doc --disable-ffplay --enable-shared --enable-avresample --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-gpl --enable-libass --enable-libfreetype --enable-libvidstab --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libxcb --enable-libx265 --enable-libxvid --enable-libx264 --enable-nonfree --enable-openssl --enable-libfdk_aac --enable-libkvazaar --enable-libaom --extra-libs=-lpthread --enable-postproc --enable-small --enable-version3 --enable-libbluray --enable-demuxer=dash --enable-decoder=hevc --enable-libxml2 --extra-cflags=-I/opt/ffmpeg/include --extra-ldflags=-L/opt/ffmpeg/lib --extra-libs=-ldl --prefix=/opt/ffmpeg
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100


  &#xA;

• Revision 29928 : On réutilise l’ancien code pour débuter notre branche

  17 juillet 2009, par kent1@… — Log

  On réutilise l’ancien code pour débuter notre branche