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• Creating GIF from QImages with ffmpeg

  17 août 2016, par Sierra

  I would like to generate GIF from QImage, using ffmpeg - all of that programmatically (C++). I’m working with Qt 5.6 and the last build of ffmpeg (build git-0a9e781 (2016-06-10).

  I’m already able to convert these QImage in .mp4 and it works. I tried to use the same principle for the GIF, changing format pixel and codec. GIF is generated with two pictures (1 second each), in 15 FPS.

  ## INITIALIZATION
  
  #####################################################################
  
  
  
  // Filepath : "C:/Users/.../qt_temp.Jv7868.gif"  
  
  // Allocating an AVFormatContext for an output format...
  
  avformat_alloc_output_context2(formatContext, NULL, NULL, filepath);
  
  
  
  ...
  
  
  
  // Adding the video streams using the default format codecs and initializing the codecs.
  
  stream = avformat_new_stream(formatContext, *codec);
  
  
  
  AVCodecContext * codecContext = avcodec_alloc_context3(*codec);
  
  
  
  context->codec_id       = codecId;
  
  context->bit_rate       = 400000;
  
  ...
  
  context->pix_fmt        = AV_PIX_FMT_BGR8;
  
  
  
  ...
  
  
  
  // Opening the codec...
  
  avcodec_open2(codecContext, codec, NULL);
  
  
  
  ...
  
  
  
  frame = allocPicture(codecContext->width, codecContext->height, codecContext->pix_fmt);
  
  tmpFrame = allocPicture(codecContext->width, codecContext->height, AV_PIX_FMT_RGBA);
  
  
  
  ...
  
  
  
  avformat_write_header(formatContext, NULL);
  
  
  
  ## ADDING A NEW FRAME
  
  #####################################################################
  
  
  
  // Getting in parameter the QImage: newFrame(const QImage & image)
  
  const qint32 width  = image.width();
  
  const qint32 height = image.height();
  
  
  
  // Converting QImage into AVFrame
  
  for (qint32 y = 0; y < height; y++) {
  
      const uint8_t * scanline = image.scanLine(y);
  
  
  
      for (qint32 x = 0; x < width * 4; x++) {
  
          tmpFrame->data[0][y * tmpFrame->linesize[0] + x] = scanline[x];
  
      }
  
  }
  
  
  
  ...
  
  
  
  // Scaling...
  
  if (codec->pix_fmt != AV_PIX_FMT_BGRA) {
  
      if (!swsCtx) {
  
          swsCtx = sws_getContext(codec->width, codec->height,
  
                                  AV_PIX_FMT_BGRA,
  
                                  codec->width, codec->height,
  
                                  codec->pix_fmt,
  
                                  SWS_BICUBIC, NULL, NULL, NULL);
  
      }
  
  
  
      sws_scale(swsCtx,
  
                (const uint8_t * const *)tmpFrame->data,
  
                tmpFrame->linesize,
  
                0,
  
                codec->height,
  
                frame->data,
  
                frame->linesize);
  
  }
  
  frame->pts = nextPts++;
  
  
  
  ...
  
  
  
  int gotPacket = 0;
  
  AVPacket packet = {0};
  
  
  
  av_init_packet(&packet);
  
  avcodec_encode_video2(codec, &packet, frame, &gotPacket);
  
  
  
  if (gotPacket) {
  
      av_packet_rescale_ts(paket, *codec->time_base, stream->time_base);
  
      paket->stream_index = stream->index;
  
  
  
      av_interleaved_write_frame(formatContext, paket);
  
  }

  But when I’m trying to modify the video codec and pixel format to match with GIF specifications, I’m facing some issues.
  I tried several codecs such as AV_CODEC_ID_GIF and AV_CODEC_ID_RAWVIDEO but none of them seem to work. During the initialization phase, avcodec_open2() always returns such kind of errors :

  Specified pixel format rgb24 is invalid or not supported
  
  Could not open video codec:  gif

  EDIT 17/06/2016

  Digging a little bit more, avcodec_open2() returns -22 :

  #define EINVAL          22      /* Invalid argument */

  EDIT 22/06/2016

  Here are the flags used to compile ffmpeg :

  "FFmpeg/Libav configuration: --disable-static --enable-shared --enable-gpl --enable-version3 --disable-w32threads --enable-nvenc --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmfx --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-libzimg --enable-lzma --enable-decklink --enable-zlib"

  Did I miss a crucial one for GIF ?

  EDIT 27/06/2016

  Thanks to Gwen, I have a first output : I setted the context->pix_fmt to AV_PIX_FMT_BGR8. Btw I’m still facing some issues with the generated GIF. It’s not playing and encoding appears to fail.

  GIF generated in command lines with ffmpeg (left) . . . GIF generated programmatically (right)
  
  

  It looks like some options are not defined... also may be a wrong conversion between QImage and AVFrame ? I updated the code above. It represents a lot of code, so I tried to stay short. Don’t hesitate to ask more details.

  End of EDIT

  I’m not really familiar with ffmpeg, any kind of help would be highly appreciated. Thank you.

• Install ffmpeg-light with cabal

  20 septembre 2016, par WirflBirfl

  I want to install the ffmpeg-light library from hackage via cabal on Windows 10 (64 bit). So I downloaded ffmpeg and extracted it to C :\FFmpeg.

  At first pkg-config was complaining that it could not find various packages. I solved this problem with .pc files.

  When I tried to use the command : cabal install ffmpeg-light cabal complained about missing C-libraries, being exactly those for which I created the .pc files.

  Then I tried the command : cabal install ffmpeg-light --extra-lib-dirs=C:\FFmpeg\lib. Now I have a different error message, which says :

  Enums.hsc:7:32: fatal error: libavcodec/avcodec.h: No such file or directory

  Edit :
  Then I tried the following command :

  cabal install ffmpeg-light --extra-lib-dirs=C:\FFmpeg\lib \
  
                             --extra-include-dirs=C:\FFmpeg\include

  Now first the compiler gives some warnings about deprecated functions in ffmpeg and redundant imports in ffmpeg-light, but compiles 11 of 11. But the build is still not successfull.

  In-place registering ffmpeg-light-0.11.1...
  
  setup-Simple-Cabal-1.22.5.0-x86_64-windows-ghc-7.10.3.exe:
  
  'C:\Haskell\bin\ghc-pkg.exe' exited with an error:
  
  ffmpeg-light-0.11.1: Warning: haddock-interfaces:
  
  C:\Users\HOLEYC~1\AppData\Local\Temp\cabal-tmp-2824\ffmpeg-light-0.11.1\dist\doc\html\ffmpeg-light\ffmpeg-light.haddock
  
  doesn't exist or isn't a file
  
  ffmpeg-light-0.11.1: Warning: haddock-html:
  
  C:\Users\HOLEYC~1\AppData\Local\Temp\cabal-tmp-2824\ffmpeg-light-0.11.1\dist\doc\html\ffmpeg-light
  
  doesn't exist or isn't a directory
  
  ffmpeg-light-0.11.1: library-dirs: C:FFmpeglib is a relative path which makes
  
  no sense (as there is nothing for it to be relative to). You can make paths
  
  relative to the package database itself by using ${pkgroot}. (use --force to
  
  override)
  
  ffmpeg-light-0.11.1: include-dirs: C:FFmpeginclude is a relative path which
  
  makes no sense (as there is nothing for it to be relative to). You can make
  
  paths relative to the package database itself by using ${pkgroot}. (use
  
  --force to override)
  
  cabal: Error: some packages failed to install:
  
  ffmpeg-light-0.11.1 failed during the building phase. The exception was:
  
  ExitFailure 1

  Some additional information :

  cabal version: cabal-install version 1.22.6.0
  
  using version 1.22.5.0 of the Cabal library
  
  gcc version of my installed Haskell platform: 5.2.0

  Example .pc file I used for pkg-config :

  Name: libavcodec
  
  Description: Library for ffmpeg
  
  Version: 57
  
  Cflags: -IC:\FFmpeg\include
  
  Libs: -LC:\FFmpeg\lib -llibavcodec

• lavfi/pan : renormalize negative gain coefficients properly

  9 octobre 2016, par Moritz Barsnick

  lavfi/pan : renormalize negative gain coefficients properly
  The parser for the outdef will accept a negative value for the first
  
  named channel’s gain. As negative values effectively only invert the
  
  phase of the signal, and not negate the level, the gains’ absolute
  
  values must be used to correctly accumulate the levels.
  Signed-off-by : Moritz Barsnick <barsnick@gmx.net>
  
  Reviewed-by : Nicolas George <george@nsup.org>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavfilter/af_pan.c