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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.

• ffmpeg : split mp3, encode aac and join produce artifacts and empty space

  18 juin 2016, par aganeiro

  Source mp3

      ffprobe -show_frames -select_streams a -print_format csv -show_entries  
  
   frame=index,pkt_dts_time ~/demo_files/000.orig.5352357791787324393.mp3
  
  frame,0.000000
  
  frame,0.026122
  
  frame,0.052245
  
  frame,0.078367

  every part I make with command, -ss position and -t time I got and calculate from previous ffprobe output

      /home/xxx/bin/ffmpeg -analyzeduration 50000000 -probesize 50000000  
  
  -ss 0.000000 -i /home/xxx/demo_files/000.orig.5352357791787324393.mp3  
  
  -s 0 -t 0.926276 -flags +global_header -c:a libfdk_aac -strict -2  
  
  -b:a 64k -ac 2 -ar 44100 -vn -f mpegts -y /tmp/p0.ts
  
  
  
      /home/xxx/bin/ffmpeg -analyzeduration 50000000 -probesize 50000000  
  
  -ss 1.018776 -i /home/xxx/demo_files/000.orig.5352357791787324393.mp 
  
  -s 0 -t 0.900153 -flags +global_header -c:a libfdk_aac -strict -2  
  
  -b:a 64k -ac 2 -ar 44100 -vn -f mpegts -y /tmp/p1.ts

  it’s produce

  [mp3 @ 0x39ca980] Estimating duration from bitrate, this may be inaccurate
  
      Input #0, mp3, from '/home/xxx/demo_files/000.orig.5352357791787324393.mp3':
  
      Duration: 00:05:17.20, start: 0.000000, bitrate: 320 kb/s
  
      Stream #0:0: Audio: mp3, 44100 Hz, stereo, s16p, 320 kb/s
  
      [mpegts @ 0x39ccea0] Using AVStream.codec to pass codec  
  
  parameters to muxers is deprecated, use AVStream.codecpar instead.
  
      [mpegts @ 0x39ccea0] frame size not set
  
      Output #0, mpegts, to '/tmp/p0.ts':
  
        Metadata:
  
          encoder         : Lavf57.38.100
  
          Stream #0:0: Audio: aac (libfdk_aac), 44100 Hz, stereo, s16, 64 kb/s
  
          Metadata:
  
            encoder         : Lavc57.46.100 libfdk_aac
  
      Stream mapping:
  
        Stream #0:0 -> #0:0 (mp3 (native) -> aac (libfdk_aac))
  
      Press [q] to stop, [?] for help
  
      size=      10kB time=00:00:00.92 bitrate=  92.3kbits/s speed=39.8x    
  
      video:0kB audio:8kB subtitle:0kB other streams:0kB global  
  
  headers:0kB muxing overhead: 24.619143%
  
        Duration: 00:00:00.63, start: 1.400000, bitrate: 127 kb/s

  Part info

      ffmpeg -hide_banner -i /tmp/p0.ts 2>&1 |grep -P 'Duration|Stream'
  
      Duration: 00:00:00.95, start: 1.400000, bitrate: 90 kb/s
  
      Stream #0:0[0x100]: Audio: aac (LC) ([15][0][0][0] / 0x000F),  
  
  44100 Hz, stereo, fltp, 68 kb/s

  Then I join all parts together with

      /home/xxx/bin/ffmpeg -i /tmp/p0.ts -i /tmp/p1.ts -i /tmp/p2.ts  
  
  -i /tmp/p3.ts -i /tmp/p4.ts -i /tmp/p5.ts -filter_complex  
  
  "[0:a]asetpts=PTS-STARTPTS[a0];[1:a]asetpts=PTS-STARTPTS[a1];  
  
  [2:a]asetpts=PTS-STARTPTS[a2];[3:a]asetpts=PTS-STARTPTS[a3];  
  
  [4:a]asetpts=PTS-STARTPTS[a4];[5:a]asetpts=PTS-STARTPTS[a5];  
  
  [a0][a1][a2][a3][a4][a5] concat=n=6:v=0:a=1 [a]"  
  
  -map [a] -strict experimental -fflags +genpts -flags +global_header  
  
  -c libfdk_aac -bsf:a aac_adtstoasc -y /tmp/res.m4a

  waveform of original and joined on the left
  

  So, as you can see joined have delays and waveforms starte later. Why ? maybe it depens that all encoded parts have start time 1.400000, ?? How to set start time to 0 on encode ?

  Also I tried to cut empty space on joining with filter_complex but result stil not good and contains artifacts because trim position looks different in every part.

      /home/xxx/bin/ffmpeg -i /tmp/p0.ts -i /tmp/p1.ts -i /tmp/p2.ts  
  
  -i /tmp/p3.ts -i /tmp/p4.ts -i /tmp/p5.ts -filter_complex  
  
  "[0:a]atrim=0.020000,asetpts=PTS-STARTPTS[a0];  
  
  [1:a]atrim=0.020000,asetpts=PTS-STARTPTS[a1];  
  
  [2:a]atrim=0.020000,asetpts=PTS-STARTPTS[a2];  
  
  [3:a]atrim=0.020000,asetpts=PTS-STARTPTS[a3];  
  
  [4:a]atrim=0.020000,asetpts=PTS-STARTPTS[a4];  
  
  [5:a]atrim=0.020000,asetpts=PTS-STARTPTS[a5];  
  
  [a0][a1][a2][a3][a4][a5] concat=n=6:v=0:a=1 [a]"  
  
  -map [a] -strict experimental -fflags +genpts  
  
  -flags +global_header -c libfdk_aac -bsf:a aac_adtstoasc  
  
  -y /tmp/res.m4a

  Whyyyy and how to solve it ?

• FFmpeg "movflags" > "faststart" causes av_write_trailer() to return -2

  30 juin 2016, par williamtroup

  I’m setting up the format layout for the ideo as follows :

  AVOutputFormat* outputFormat = ffmpeg.av_guess_format(null, "output.mp4", null);
  
  
  
  AVCodec* videoCodec = ffmpeg.avcodec_find_encoder(outputFormat->video_codec);
  
  
  
  AVFormatContext* formatContext = ffmpeg.avformat_alloc_context();
  
  formatContext->oformat = outputFormat;
  
  formatContext->video_codec_id = videoCodec->id;
  
  
  
  ffmpeg.avformat_new_stream(formatContext, videoCodec);

  This is how I am setting up the Codec Context :

  AVCodecContext* codecContext = ffmpeg.avcodec_alloc_context3(videoCodec);
  
  codecContext->bit_rate = 400000;
  
  codecContext->width = 1280;
  
  codecContext->height = 720;
  
  codecContext->gop_size = 12;
  
  codecContext->max_b_frames = 1;
  
  codecContext->pix_fmt = videoCodec->pix_fmts[0];
  
  codecContext->codec_id = videoCodec->id;
  
  codecContext->codec_type = videoCodec->type;
  
  codecContext->time_base = new AVRational
  
  {
  
      num = 1,
  
      den = 30
  
  };

  I’m using the following code to setup the "movflags" > "faststart" option for the header of the video :

  AVDictionary* options = null;
  
  
  
  int result = ffmpeg.av_dict_set(&options, "movflags", "faststart", 0);
  
  
  
  int writeHeaderResult = ffmpeg.avformat_write_header(formatContext, &options);

  The file is opened and the header is written as follows :

  if ((formatContext->oformat->flags & ffmpeg.AVFMT_NOFILE) == 0)
  
  {
  
      int ioOptionResult = ffmpeg.avio_open(&formatContext->pb, "output.mp4", ffmpeg.AVIO_FLAG_WRITE);
  
  }
  
  
  
  int writeHeaderResult = ffmpeg.avformat_write_header(formatContext, &options);

  After this, I write each video frame as follows :

  outputFrame->pts = frameIndex;
  
  
  
  packet.flags |= ffmpeg.AV_PKT_FLAG_KEY;
  
  packet.pts = frameIndex;
  
  packet.dts = frameIndex;
  
  
  
  int encodedFrame = 0;
  
  int encodeVideoResult = ffmpeg.avcodec_encode_video2(codecContext, &packet, outputFrame, &encodedFrame);
  
  
  
  if (encodedFrame != 0)
  
  {
  
      packet.pts = ffmpeg.av_rescale_q(packet.pts, codecContext->time_base, m_videoStream->time_base);
  
      packet.dts = ffmpeg.av_rescale_q(packet.dts, codecContext->time_base, m_videoStream->time_base);
  
      packet.stream_index = m_videoStream->index;
  
  
  
      if (codecContext->coded_frame->key_frame > 0)
  
      {
  
          packet.flags |= ffmpeg.AV_PKT_FLAG_KEY;
  
      }
  
  
  
      int writeFrameResult = ffmpeg.av_interleaved_write_frame(formatContext, &packet);
  
  }

  After that, I write the trailer :

  int writeTrailerResult = ffmpeg.av_write_trailer(formatContext);

  However, writeTrailerResult is always -2. I’m been looking into this problem for days and cannot figure out what the problem is.

  The DLLs used for the AutoGen library are :

  avcodec-56.dll
  
  avdevice-56.dll
  
  avfilter-5.dll
  
  avformat-56.dll
  
  avutil-54.dll
  
  postproc-53.dll
  
  swresample-1.dll
  
  swscale-3.dll