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• Creating video thumbnail with ffmpeg from buffer

  28 juillet 2021, par J. Carpenter

  Attempting to create a child process which spawns ffmpeg command. Should use the buffer from fs.readFile to write to stdin. The -i - flag tells ffmpeg to source input from stdin but nothing is happening when running this code.

  


  If replace -i - with -i test.mp4 this script works perfectly.

  


  What is wrong with the write to stdin which is not allowing code to generate thumbnail ?

  


  (async () => {
    const spawn = require('child_process').spawn;
    const fs = require('fs/promises');
    const buffer = await fs.readFile('test.mp4');
    await new Promise((resolve) => {
        console.log('Spawning process');
        const process = spawn('ffmpeg',
            [
                '-ss', '00:00:01',
                '-i', '-',
                '-s', '256x256',
                '-vframes', '1',
                '-f', 'image2',
                'output.png'
            ]);
        process.stdin.write(buffer);
        process.stdin.end();
        process.on('close', (done) => {
            console.log("Process closed: ", done);
            resolve();
        });
    });
})();


  


  Edit :

  


  Also tried this :

  


  const ffmpeg = require('fluent-ffmpeg');
module.exports =
    async (stream) => {
        ffmpeg(stream)
        .addOption('-f','rawvideo')
        .inputFormat('mov')
        .toFormat('mp4')
        .thumbnail({
            count:1,
            size:'256x256',
            filename:'test.png',
            timemarks:["00:00:03"]
        })
        .on('stdout',(stdout)=>{
            console.log(stdout);
        })
        .on('stderr',(err)=>{
            console.log(err);
        });
    }


  


  With this error output :

  


  ffmpeg version N-102781-g05f9b3a0a5 Copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 10-win32 (GCC) 20210408
  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-gpl --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 --enable-libvmaf --enable-vulkan --enable-amf --enable-libaom --enable-avisynth --enable-libdav1d --enable-libdavs2 --disable-libfdk-aac --enable-ffnvcodec --enable-cuda-llvm --enable-libglslang --enable-libgme --enable-libass --enable-libbluray --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvpx --enable-libwebp --enable-lv2 --enable-libmfx --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librav1e --enable-librubberband --enable-schannel --enable-sdl2 --enable-libsoxr --enable-libsrt --enable-libsvtav1 --enable-libtwolame --enable-libuavs3d --enable-libvidstab --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libzimg --extra-cflags=-DLIBTWOLAME_STATIC --extra-cxxflags= --extra-ldflags=-pthread --extra-ldexeflags= --extra-libs=-lgomp
  libavutil      57.  0.100 / 57.  0.100
  libavcodec     59.  1.102 / 59.  1.102
  libavformat    59.  3.101 / 59.  3.101
  libavdevice    59.  0.100 / 59.  0.100
  libavfilter     8.  0.102 /  8.  0.102
  libswscale      6.  0.100 /  6.  0.100
  libswresample   4.  0.100 /  4.  0.100
  libpostproc    56.  0.100 / 56.  0.100
[mov,mp4,m4a,3gp,3g2,mj2 @ 0000025220812340] stream 0, offset 0x24: partial file
[mov,mp4,m4a,3gp,3g2,mj2 @ 0000025220812340] Could not find codec parameters for stream 1 (Video: h264 (avc1 / 0x31637661), none(bt709), 640x360, 2630 kb/s): unspecified pixel format
Consider increasing the value for the 'analyzeduration' (0) and 'probesize' (5000000) options
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'pipe:0':
  Metadata:
    major_brand     : qt
    minor_version   : 0
    compatible_brands: qt
    creation_time   : 2021-07-25T11:06:03.000000Z
  Duration: 00:00:17.38, start: 0.000000, bitrate: N/A
  Stream #0:0(und): Audio: aac (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 127 kb/s (default)
    Metadata:
      creation_time   : 2021-07-25T11:06:03.000000Z
      handler_name    : Core Media Audio
      vendor_id       : [0][0][0][0]
  Stream #0:1(und): Video: h264 (avc1 / 0x31637661), none(bt709), 640x360, 2630 kb/s, 29.98 fps, 29.97 tbr, 600 tbn (default)     
    Metadata:
      creation_time   : 2021-07-25T11:06:03.000000Z
      handler_name    : Core Media Video
      vendor_id       : [0][0][0][0]
      encoder         : H.264
  Stream #0:2(und): Data: none (mebx / 0x7862656D), 0 kb/s (default)
    Metadata:
      creation_time   : 2021-07-25T11:06:03.000000Z
      handler_name    : Core Media Metadata
  Stream #0:3(und): Data: none (mebx / 0x7862656D), 0 kb/s (default)
    Metadata:
      creation_time   : 2021-07-25T11:06:03.000000Z
      handler_name    : Core Media Metadata
Stream mapping:
  Stream #0:1 (h264) -> scale
  split -> Stream #0:0 (libx264)
[mov,mp4,m4a,3gp,3g2,mj2 @ 0000025220812340] stream 1, offset 0xb1bf9: partial file
pipe:0: Invalid data found when processing input
Cannot determine format of input stream 0:1 after EOF
Error marking filters as finished
Conversion failed!

events.js:292
      throw er; // Unhandled 'error' event
      ^

Error: ffmpeg exited with code 1: pipe:0: Invalid data found when processing input
Cannot determine format of input stream 0:1 after EOF
Error marking filters as finished
Conversion failed!


  


• libvorbis complains “more samples than frame size”

  11 août 2021, par Yoz

  I am trying to figure out what's wrong with my command to encode into theora+vorbis. I am able to demonstrate the issue with minimum code as following :

  


  encoding audio followed by video works ok :

  


  ffmpeg -filter_complex "smptehdbars=size=1280x720:rate=30000/1001[v];sine=beep_factor=2[a]" -map [a] -map [v] -vcodec libtheora -acodec libvorbis -t 3 -f ogg map-audio-video.ogg -y


  


  however video followed by audio does not work (swapped order of -map) :

  


  ffmpeg -filter_complex "smptehdbars=size=1280x720:rate=30000/1001[v];sine=beep_factor=2[a]" -map [v] -map [a] -vcodec libtheora -acodec libvorbis -t 3 -f ogg map-video-audio.ogg -y


  


  and fails with the following error :

  


  ffmpeg version 4.4-full_build-www.gyan.dev Copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 10.2.0 (Rev6, Built by MSYS2 project)
Stream mapping:
  smptehdbars -> Stream #0:0 (libtheora)
  sine -> Stream #0:1 (libvorbis)
Press [q] to stop, [?] for help
[libvorbis @ 000001f846602fc0] more samples than frame size
Audio encoding failed
Conversion failed!


  


  Any idea why the standard order video, audio breaks on samples vs. frame size ?

  


• How to make ffmpeg re-encode an vp9 webm with alpha into a vp9 webm with alpha

  28 juillet 2021, par LemmeTestThat

  I am trying to find optimal parameters for encoding a transparent video using ffmpeg in my scenario, and as a test, I have been re-encoding a pre-made transparent .webm (vp9 with alpha channel, made using python vidgear) like this :

  


  $ /usr/bin/ffmpeg -i pre-made.webm pre-made-remade.webm
ffmpeg version 4.3.2-0york0~18.04 Copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 7 (Ubuntu 7.5.0-3ubuntu1~18.04)
  configuration: --prefix=/usr --extra-version='0york0~18.04' --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-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-libzimg --enable-pocketsphinx --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, matroska,webm, from 'pre-made.webm':
  Metadata:
    ENCODER         : Lavf58.45.100
  Duration: 00:01:11.04, start: 0.000000, bitrate: 1107 kb/s
    Stream #0:0: Video: vp9 (Profile 0), yuv420p(tv), 1514x1910, SAR 1:1 DAR 757:955, 25 fps, 25 tbr, 1k tbn, 1k tbc (default)
    Metadata:
      alpha_mode      : 1
      ENCODER         : Lavc58.91.100 libvpx-vp9
      DURATION        : 00:01:11.040000000
Stream mapping:
  Stream #0:0 -> #0:0 (vp9 (native) -> vp9 (libvpx-vp9))
Press [q] to stop, [?] for help
[libvpx-vp9 @ 0x55927254b0c0] v1.7.0
[libvpx-vp9 @ 0x55927254b0c0] Neither bitrate nor constrained quality specified, using default CRF of 32
Output #0, webm, to 'pre-made-remade.webm':
  Metadata:
    encoder         : Lavf58.45.100
    Stream #0:0: Video: vp9 (libvpx-vp9), yuv420p, 1514x1910 [SAR 1:1 DAR 757:955], q=-1--1, 25 fps, 1k tbn, 25 tbc (default)
    Metadata:
      alpha_mode      : 1
      DURATION        : 00:01:11.040000000
      encoder         : Lavc58.91.100 libvpx-vp9
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: N/A
frame= 1776 fps=8.9 q=0.0 Lsize=    6159kB time=00:01:11.00 bitrate= 710.6kbits/s speed=0.354x
video:6146kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.214488%


  


  According to the ffmpeg logs, the libvpx-vp9 is correctly being chosen, and alpha_mode is 1, which bodes well.
However, when actually viewing the video, the video is no longer trasparent.

  


  How could I force ffmpeg to keep the alpha channel when re-encoding the video ? (This also applies when trying to merge audio into the .webm)

  


  Bonus question : what arguments do you recommend for efficient vp9 encoding ? I have tried using -threads 16 -speed 4 -tile-columns 6 -frame-parallel 1 -row-mt 1 but it seems to fail at fully utilizing all my CPU cores when encoding with the alpha channel (when piping frames from my python script).