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• How to send encoded video (or audio) data from server to client in a way that's decodable by webcodecs API using minimal latency and data overhead

  11 janvier 2023, par Tiger Yang

  My question (read entire post for context) :

  


  Given the unique circumstance of only ever decoding data from a specifically-configured encoder, what is the best way I can send the encoded bitstream along with the bare minimum extra bytes required to properly configure the decoder on the client's end (including only things that change per stream, and omitting things that don't, such as resolution) ? I'm a sucker for zero compromises, and I think I am willing to design my own minimal container format to accomplish this.

  


  Context and problem :

  


  I'm working on a remote desktop implementation that consists of a server that captures and encodes the display and speakers using FFmpeg and forwards it via pipe to a go (language) program which sends it on two unidirectional webtransport streams to my client, which I plan to decode using the webcodecs API. According to MDN, the video decoder needs to be fed via .configure() an object containing the following : https://developer.mozilla.org/en-US/docs/Web/API/VideoDecoder/configure before it's able to decode anything.

  


  same goes for the audio decoder : https://developer.mozilla.org/en-US/docs/Web/API/AudioDecoder/configure

  


  What I've tried so far :

  


  Because this remote desktop will be for my personal use only, it would only ever receive streams from a specific encoder configured in a specific way encoding video at a specific resolution, framerate, color space, etc.. Therefore, I took my video capture FFmpeg command...

  


  videoString := []string{
        "ffmpeg",
        "-init_hw_device", "d3d11va",
        "-filter_complex", "ddagrab=video_size=1920x1080:framerate=60",
        "-vcodec", "hevc_nvenc",
        "-tune", "ll",
        "-preset", "p7",
        "-spatial_aq", "1",
        "-temporal_aq", "1",
        "-forced-idr", "1",
        "-rc", "cbr",
        "-b:v", "500K",
        "-no-scenecut", "1",
        "-g", "216000",
        "-f", "hevc", "-",
    }


  


  ...and instructed it to write to an mp4 file instead of outputting to pipe, and then I had this webcodecs demo https://w3c.github.io/webcodecs/samples/video-decode-display/ demux it using mp4box.js. Knowing that the demo outputs a proper .configure() object, I blindly copied it and had my client configure using that every time. Sadly, it didn't work, and I since noticed that the "description" part of the configure object changes despite the encoder and parameters being the same.

  


  I knew that mp4 files worked via mp4box, but they can't be streamed with low latency over a network, and additionally, ffmpeg's -f parameters specifies the muxer to use, but there are so many different types.

  


  At this point, I think I'm completely out of my depth, so :

  


  Given the unique circumstance of only ever decoding data from a specifically-configured encoder, what is the best way I can send the encoded bitstream along with the bare minimum extra bytes required to properly configure the decoder on the client's end (including only things that change per stream, and omitting things that don't, such as resolution) ? I'm a sucker for zero compromises, and I think I am willing to design my own minimal container format to accomplish this. (copied above)

  


• How much of modern FFmpeg is written by Fabrice Bellard ?

  17 décembre 2022, par Hashim Aziz

  FFmpeg is considered by many to be the work of Fabrice Bellard, and maybe even his magnum opus, but since he stopped contributing to the project (under the pseudonym Gérard Lantau) in 2004, I wondered how much of it can actually still be said to be his. By comparison, Linus Torvalds' Wikipedia page states :

  


  


  As of 2006, approximately 2% of the Linux kernel was written by
Torvalds himself.[28] Because thousands have contributed to it, his
percentage is still one of the largest. However, he said in 2012 that
his own personal contribution is now mostly merging code written by
others, with little programming.

  


  


  This despite the fact that Torvalds is still an active contributor to the Linux kernel, whereas Bellard hasn't been an active contributor to FFmpeg for almost two decades.

  


  FFmpeg being an open-source project tracked with Git, it seems like the question should be technically and objectively answerable, but as someone who hates mailing lists and the generally archaic ways that big open-source projects like to do things, I wouldn't know where to start in doing so.

  


  Just how much of the modern FFmpeg codebase is Fabrice Bellard actually responsible for, in comparison to the other FFmpeg devs ?

  


• FFMPEG sidechaincompress error initializing complex filters with invalid argument

  15 août 2022, par DevDevRun

  I am using FFMPEG to convert process various audio files.
When using the sidechaincompress filter, I found this command line to work on my personal Windows 10 machine but not working anymore on our Debian server.
Maybe this command is not working anymore on newer version, or am I missing something (a «’» in the commande line, or a package ?) on our Linux server ? We definitely need to use this sidechaincompress filter with two audio files « Assets » and « Main ».

  


  Here is the command we run :

  


  FFMPEG -i /var/asset.flac -i /var/main.flac -filter_complex "[1:a]asplit=2[sc][mix];[0:a][sc]sidechaincompress=threshold=0.05:ratio=11:release:3000[compr];[compr][mix]amix=normalize=0" /var/sidechain.flacs


  


  Linux version : ffmpeg version 4.3.4-0+deb11u1

  


  and it returns :

  


  ffmpeg version 4.3.4-0+deb11u1 Copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 10 (Debian 10.2.1-6)
  configuration: --prefix=/usr --extra-version=0+deb11u1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librabbitmq --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-pocketsphinx --enable-libmfx --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
  libavutil      56. 51.100 / 56. 51.100
  libavcodec     58. 91.100 / 58. 91.100
  libavformat    58. 45.100 / 58. 45.100
  libavdevice    58. 10.100 / 58. 10.100
  libavfilter     7. 85.100 /  7. 85.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  7.100 /  5.  7.100
  libswresample   3.  7.100 /  3.  7.100
  libpostproc    55.  7.100 / 55.  7.100
Input #0, flac, from '/var/asset.flac':
  Metadata:
    encoder         : Lavf59.25.100
  Duration: 00:02:33.65, start: 0.000000, bitrate: 760 kb/s
    Stream #0:0: Audio: flac, 44100 Hz, stereo, s32 (24 bit)
Input #1, flac, from '/var/2-main.flac':
  Metadata:
    encoder         : Lavf58.45.100
  Duration: 00:02:33.65, start: 0.000000, bitrate: 1093 kb/s
    Stream #1:0: Audio: flac, 44100 Hz, stereo, s32 (24 bit)
[sidechaincompress @ 0x5622749721c0] [Eval @ 0x7fff94caf520] Undefined constant or missing '(' in 'release'
[sidechaincompress @ 0x5622749721c0] Unable to parse option value "release"
[sidechaincompress @ 0x5622749721c0] Value 3000.000000 for parameter 'mode' out of range [0 - 1]
[sidechaincompress @ 0x5622749721c0] [Eval @ 0x7fff94caf550] Undefined constant or missing '(' in 'release'
[sidechaincompress @ 0x5622749721c0] Unable to parse option value "release"
[sidechaincompress @ 0x5622749721c0] Error setting option level_in to value release.
[Parsed_sidechaincompress_1 @ 0x5622749720c0] Error applying options to the filter.
[AVFilterGraph @ 0x56227493ea40] Error initializing filter 'sidechaincompress' with args 'threshold=0.05:ratio=11:release:3000'
Error initializing complex filters.
Invalid argument