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• FFMpeg, libav, Problem with sws_scale and yuv to rgb conversion - colors are not correct

  7 juillet 2022, par Milika

  I've been trying to create my own video player in Delphi, and ffmpeg works great, until i hit a snag with color spaces, or color conversion.

  


  Been trying everything for a couple of days, but can't figure it out.
I'm using AV_PIX_FMT_RGB48LE as output...

  


  Old context creation :

  


        videoConvContext := sws_getContext(AVStreamInit.codec.width, AVStreamInit.codec.height, AVStreamInit.codec.pix_fmt, AVStreamInit.codec.width, AVStreamInit.codec.height, AV_PIX_FMT_RGB48LE, SWS_POINT, nil, nil, nil);


  


  New context creation :

  


      dstRange := 1;
    srcRange := 1;
    if AVStreamInit.codec.color_range = AVCOL_RANGE_MPEG then
      srcRange := 0;

    videoConvContext := sws_alloc_context();

    av_opt_set_int(videoConvContext, 'sws_flags', SWS_POINT or SWS_PRINT_INFO, 0);

    av_opt_set_int(videoConvContext, 'srcw', AVStreamInit.codec.width, 0);
    av_opt_set_int(videoConvContext, 'srch', AVStreamInit.codec.height, 0);
    av_opt_set_int(videoConvContext, 'src_format', Integer(AVStreamInit.codec.pix_fmt), 0);

    av_opt_set_int(videoConvContext, 'dstw', AVStreamInit.codec.width, 0);
    av_opt_set_int(videoConvContext, 'dsth', AVStreamInit.codec.height, 0);
    av_opt_set_int(videoConvContext, 'dst_format', Integer(AV_PIX_FMT_RGB48LE), 0);

    i1 := sws_getCoefficients2(Integer(AVStreamInit.codec.colorspace));
    i2 := sws_getCoefficients2(SWS_CS_ITU709);

    ret := sws_setColorspaceDetails2(videoConvContext, i1, srcRange, i2, dstRange, 0, 1 shl 16, 1 shl 16);

    sws_init_context(videoConvContext, nil, nil);


  


  Results are exactly the same....

  


  Output from sws_scale does not have correct colors, here are 2 screenshot

  


  ok - from mpc-hc


  


  not ok - from my player via sws_scale (direct raw extract so no color processing done)


  


  This video has pix_fmt AV_PIX_FMT_YUV420P10LE, but it happens on other YUV inputs, but not so obvious. Also on other RGB outputs(8bit etc)...
Here the Netflix logo is pure red, but sws_scale output gives orange-ish...

  


  Sws_scale code just for reference :

  


  sws_scale(videoConvContext, @AVPacketBuffer.AVFrameCopy.Data, @AVPacketBuffer.AVFrameCopy.linesize, 0, AVStream.codec.height, @BitmapXBuffer.data, @linesize);


  


  BitmapXBuffer.data is a signle buffer of correct size...

  


  AVFrameCopy - is a copy of original frame done with :

  


    if Assigned(AVPacketBuffer.AVFrameCopy) then
      av_frame_free(@AVPacketBuffer.AVFrameCopy);

    AVPacketBuffer.AVFrameCopy := av_frame_alloc();
    AVPacketBuffer.AVFrameCopy.format := AVPacketBuffer.AVFrame.format;
    AVPacketBuffer.AVFrameCopy.width := AVPacketBuffer.AVFrame.width;
    AVPacketBuffer.AVFrameCopy.height := AVPacketBuffer.AVFrame.height;
    AVPacketBuffer.AVFrameCopy.channels := AVPacketBuffer.AVFrame.channels;
    AVPacketBuffer.AVFrameCopy.channel_layout := AVPacketBuffer.AVFrame.channel_layout;
    AVPacketBuffer.AVFrameCopy.nb_samples := AVPacketBuffer.AVFrame.nb_samples;
    av_frame_get_buffer(AVPacketBuffer.AVFrameCopy, 32);
    av_frame_copy(AVPacketBuffer.AVFrameCopy, AVPacketBuffer.AVFrame);
    av_frame_copy_props(AVPacketBuffer.AVFrameCopy, AVPacketBuffer.AVFrame);


  


  Thanks !

  


• ffmpeg : Unrecognized option 'alpha_quality'

  16 avril 2024, par László Monda

  I want to make transparent videos work in Safari, which doesn't support WebM for this purpose but only H265 with alpha transparency.

  


  According to this post, I used Shutter Encoder, but only some of its versions work for this purpose on Mac.

  


  Instead of using Shutter Encoder on Mac, I want to use ffmpeg on my Linux PC. Shutter Encoder uses the following command in the background :

  


  ffmpeg -threads 0 -hwaccel none -i input.mov -c:v hevc_videotoolbox -alpha_quality 1 -b:v 1000k -profile:v main -level 5.2 -map v:0 -an -pix_fmt yuva420p -sws_flags bicubic -tag:v hvc1 -metadata creation_time=2024-04-14T14:53:08.734684Z -y output.mp4

  


  which yields the following output on my PC :

  


  ffmpeg version 4.4.2-0ubuntu0.22.04.1 Copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 11 (Ubuntu 11.2.0-19ubuntu1)
  configuration: --prefix=/usr --extra-version=0ubuntu0.22.04.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --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-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-pocketsphinx --enable-librsvg --enable-libmfx --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
  WARNING: library configuration mismatch
  avcodec     configuration: --prefix=/usr --extra-version=0ubuntu0.22.04.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --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-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-pocketsphinx --enable-librsvg --enable-libmfx --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared --enable-version3 --disable-doc --disable-programs --enable-libaribb24 --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libtesseract --enable-libvo_amrwbenc --enable-libsmbclient
  libavutil      56. 70.100 / 56. 70.100
  libavcodec     58.134.100 / 58.134.100
  libavformat    58. 76.100 / 58. 76.100
  libavdevice    58. 13.100 / 58. 13.100
  libavfilter     7.110.100 /  7.110.100
  libswscale      5.  9.100 /  5.  9.100
  libswresample   3.  9.100 /  3.  9.100
  libpostproc    55.  9.100 / 55.  9.100
Unrecognized option 'alpha_quality'.
Error splitting the argument list: Option not found


  


  When googling for "Unrecognized option 'alpha_quality'.", there are no results, which I find very odd.

  


  What's going on, and how can I make ffmpeg work for this purpose without Shutter Encoder ?

  


• Evolution #4148 : Augmenter la largeur de l’espace privé

  6 février 2020, par tcharlss (*´_ゝ｀)

  Hop je reprends le fil du ticket.

  Pour rappel entre temps, il y a eu un fil de discussion sur feu la liste spip-zone : https://www.mail-archive.com/spip-zone@rezo.net/msg48847.html

  Donc suite à cette discussion, voilà une proposition d’implémentation qui reprend ce dont on avait parlé : https://git.spip.net/spip/spip/pulls/17

  Alors pour celleux qui veulent tester mais ont la flemme d’installer localement, il y a un site de test ici : https://dev.mukt.fr/labo/prive_large/ecrire/ (il y aura un 404 la 1ère fois : virer le slash en trop après mukt.fr, recharger et ça sera bon).
  J’hésite un peu à lâcher les identifiants dans la nature même si ce n’est qu’un site de test, faites une demande en mp.

  Quelques précisions en plus du descriptif du PR :

  - J’ai poussé à 1500px, mais on peut revenir à 1400px si ça paraît trop.
  - Pour le support des vieux navigateurs : ça a été testé sur un vieux safari qui ne supporte pas les CSS grid, et nicod_ a regardé sur IE9. À priori c’est bon mais d’autres tests seraient souhaitables.