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• ffmpeg : missing frames with mp4 encoding

  6 juillet 2016, par Sierra

  I’m currently developing a desktop app that generates videos from pictures (QImage to be more specific). I’m working with Qt 5.6 and the last build of ffmpeg (build git-0a9e781 (2016-06-10)).

  I encode severals QImage to create an .mp4 video. I already have an output but it seems that some frames are missing.

  Here is my code. I tried to be as clear as possible, removing comments and errors catching.

  ## INITIALIZATION
  
  #####################################################################
  
  
  
  AVOutputFormat  * outputFormat  = Q_NULLPTR;
  
  AVFormatContext * formatContext = Q_NULLPTR;
  
  
  
  // filePath: "C:/Users/.../qt_temp.Jv7868.mp4" 
  
  avformat_alloc_output_context2(&formatContext, NULL, NULL, filePath.data());
  
  
  
  outputFormat = formatContext->oformat;
  
  if (outputFormat->video_codec != AV_CODEC_ID_NONE) {
  
      // Finding a registered encoder with a matching codec ID...
  
      *codec = avcodec_find_encoder(outputFormat->video_codec);
  
  
  
      // Adding a new stream to a media file...
  
      stream = avformat_new_stream(formatContext, *codec);
  
      stream->id = formatContext->nb_streams - 1;
  
  
  
  
  
      AVCodecContext * codecContext = avcodec_alloc_context3(*codec);
  
  
  
      switch ((*codec)->type) {
  
      case AVMEDIA_TYPE_VIDEO:
  
          codecContext->codec_id  = outputFormat->video_codec;
  
          codecContext->bit_rate  = 400000;
  
  
  
          codecContext->width     = 1240;
  
          codecContext->height    = 874;
  
  
  
          // Timebase: this is the fundamental unit of time (in seconds) in terms of which frame
  
          // timestamps are represented. For fixed-fps content, timebase should be 1/framerate
  
          // and timestamp increments should be identical to 1.
  
          stream->time_base       = (AVRational){1, 24};
  
          codecContext->time_base = stream->time_base;
  
  
  
          // Emit 1 intra frame every 12 frames at most
  
          codecContext->gop_size  = 12;
  
          codecContext->pix_fmt   = AV_PIX_FMT_YUV420P;
  
  
  
          if (codecContext->codec_id == AV_CODEC_ID_H264) {
  
              av_opt_set(codecContext->priv_data, "preset", "slow", 0);
  
          }
  
          break;
  
      }
  
  
  
      if (formatContext->oformat->flags & AVFMT_GLOBALHEADER) {
  
          codecContext->flags |= CODEC_FLAG_GLOBAL_HEADER;
  
      }
  
  }
  
  
  
  avcodec_open2(codecContext, codec, NULL);
  
  
  
  // Allocating and initializing a re-usable frames...
  
  frame = allocPicture(codecContext->width, codecContext->height, codecContext->pix_fmt);
  
  tmpFrame = allocPicture(codecContext->width, codecContext->height, AV_PIX_FMT_BGRA);
  
  
  
  avcodec_parameters_from_context(stream->codecpar, codecContext);
  
  
  
  av_dump_format(formatContext, 0, filePath.data(), 1);
  
  
  
  if (!(outputFormat->flags & AVFMT_NOFILE)) {
  
      avio_open(&formatContext->pb, filePath.data(), AVIO_FLAG_WRITE);
  
  }
  
  
  
  // Writing the stream header, if any...
  
  avformat_write_header(formatContext, NULL);
  
  
  
  ## RECEIVING A NEW FRAME
  
  #####################################################################
  
  
  
  // New QImage received: QImage image
  
  const qint32 width  = image.width();
  
  const qint32 height = image.height();
  
  
  
  // When we pass a frame to the encoder, it may keep a reference to it internally;
  
  // make sure we do not overwrite it here!
  
  av_frame_make_writable(tmpFrame);
  
  
  
  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];
  
      }
  
  }
  
  
  
  // As we only generate a BGRA picture, we must convert it to the
  
  // codec pixel format if needed.
  
  if (!swsCtx) {
  
      swsCtx = sws_getContext(width, height,
  
                              AV_PIX_FMT_BGRA,
  
                              codecContext->width, codecContext->height,
  
                              codecContext->pix_fmt,
  
                              swsFlags, NULL, NULL, NULL);
  
  }
  
  
  
  sws_scale(swsCtx,
  
            (const uint8_t * const *)tmpFrame->data,
  
            tmpFrame->linesize,
  
            0,
  
            codecContext->height,
  
            frame->data,
  
            frame->linesize);
  
  
  
  ...
  
  
  
  AVFrame * frame = Q_NULLPTR;
  
  int gotPacket = 0;
  
  
  
  av_init_packet(&packet);
  
  
  
  // Packet data will be allocated by the encoder
  
  this->packet.data = NULL;
  
  this->packet.size = 0;
  
  
  
  frame->pts = nextPts++; // nextPts starts to 0
  
  avcodec_encode_video2(codecContext, &packet, frame, &gotPacket);
  
  
  
  if (gotPacket) {
  
      if (codecContext->coded_frame->key_frame) {
  
         packet.flags |= AV_PKT_FLAG_KEY;
  
      }
  
  
  
      // Rescale output packet timestamp values from codec to stream timebase
  
      av_packet_rescale_ts(packet, *codecContext->time_base, stream->time_base);
  
      packet->stream_index = stream->index;
  
  
  
      // Write the compressed frame to the media file.
  
      av_interleaved_write_frame(formatContext, packet);
  
  
  
      av_packet_unref(&this->packet);
  
  }
  
  
  
  ## FINISHING ENCODING
  
  #####################################################################
  
  
  
  // Retrieving delayed frames if any...
  
  for (int gotOutput = 1; gotOutput;) {
  
      avcodec_encode_video2(codecContext, &packet, NULL, &gotOutput);
  
  
  
      if (gotOutput) {
  
          // Rescale output packet timestamp values from codec to stream timebase
  
          av_packet_rescale_ts(packet, *codecContext->time_base, stream->time_base);
  
          packet->stream_index = stream->index;
  
  
  
          // Write the compressed frame to the media file.
  
          av_interleaved_write_frame(formatContext, packet);
  
          av_packet_unref(&packet);
  
      }
  
  }
  
  
  
  av_write_trailer(formatContext);
  
  
  
  avcodec_free_context(&codecContext);
  
  av_frame_free(&frame);
  
  av_frame_free(&tmpFrame);
  
  sws_freeContext(swsCtx);
  
  
  
  if (!(outputFormat->flags & AVFMT_NOFILE)) {
  
      // Closing the output file...
  
      avio_closep(&formatContext->pb);
  
  }
  
  
  
  avformat_free_context(formatContext);

  A part of the last second is always cut (e.g. when I send 48 frames, 24 fps, media players show 1,9 seconds of the video). I analyzed the video (48 frames, 24fps) with ffmpeg in command line, and I found something weird :
  
  When I re encode the video with ffmpeg (in command line) to the same format, I get a more logical output :
  

  From what I rode on different topics, I think it is closely connected to the h264 codec but I have no idea how to fix it. I’m not familiar with ffmpeg so any kind of help would be highly appreciated. Thank you.

  EDIT 06/07/2016
  Digging a little bit more in ffmpeg examples, I noticed these lines when closing the media file :

  uint8_t endcode[] = { 0, 0, 1, 0xb7 };
  
  ...
  
  /* add sequence end code to have a real mpeg file */
  
  fwrite(endcode, 1, sizeof(endcode), f);

  Is that sequence could be linked to my problem ? I’m trying to implement this to my code but, for now, it corrupts the media file. Any idea on how can I implement that line for my case ?

• Anomalie #3707 : bug dans la gestion des langues avec le multilinguisme : impossible de fixer la t...

  30 juin 2016, par Guillaume Fahrner

  le patch demandé sur IRC :

  
  — - prive/formulaires/traduire.php      2016-03-10 15:32:38.000000000 +0100
  +++ /var/www/www.root-me.org/htdocs/prive/formulaires/traduire.php      2016-05-26 09:27:03.194473328 +0200
  @@ -154,7 +154,8 @@
          if (!_request(’annuler’) and autoriser(’changerlangue’, $objet, $id_objet)) 
                  // action/editer_xxx doit traiter la modif de changer_lang
                  $res = formulaires_editer_objet_traiter($objet, $id_objet, 0, 0, $retour) ;
  
   
  +        
  +        if (!_request(’annuler’) and autoriser(’changertraduction’, $objet, $id_objet)) 
                  if ($id_trad = _request(’id_trad’) or _request(’supprimer_trad’)) 
                          $referencer_traduction = charger_fonction(’referencer_traduction’, ’action’) ;
                          $referencer_traduction($objet, $id_objet, intval($id_trad)) ; // 0 si supprimer_trad
  @@ -166,7 +167,7 @@
                          $_id_table_objet = id_table_objet($objet) ;
                          if ($id_trad = sql_getfetsel(’id_trad’, $table_objet_sql, "$_id_table_objet=" . intval($id_objet))) 
                                  $referencer_traduction = charger_fonction(’referencer_traduction’, ’action’) ;
  
   $referencer_traduction($objet, $id_trad, $new_id_trad) ;
  +                               $res = $referencer_traduction($objet, $id_trad, $new_id_trad) ;
                          
                  
          
  
  — - prive/formulaires/traduire.html     2016-03-10 15:32:38.000000000 +0100
  +++ /var/www/www.root-me.org/htdocs/prive/formulaires/traduire.html     2016-05-26 09:31:39.834465138 +0200
  @@ -24,7 +24,7 @@
                                                          f.find(’.boutons,.new_trad,.editer_id_trad’).show(’fast’) ;
                                                          f.find(’#changer_lang’).eq(0).focus() ;return false ;" 
                                                  ><:bouton_changer :> \([(#ENV_langue| ?[(#ENV_objet|objet_infotexte_langue_objet|_T)],<:info_traductions :>)]\)&#93 ;
  
   [(#ENV_langue|oui)
  +                                       [(#ENVeditable|oui)
                                          [(#ENV{_saisie_en_cours}">
                                          (#INCLUREfond=formulaires/inc-options-langues,name=changer_lang,default=#ENV**_langue,herit=#ENV**langue_parent)
                                          ]]]

• FFMPEG : Video file to YUV conversion by binary ffmpeg and by code C++ give different results

  30 juin 2016, par Anny G

  Disclaimer : I have looked at the following question,
  FFMPEG : RGB to YUV conversion by binary ffmpeg and by code C++ give different results
  but it didn’t help and it is not applicable to me because I am not using SwsContext or anything.

  Following first few tutorials by http://dranger.com/ffmpeg/, I have created a simple program that reads a video, decodes it and then when the frame is decoded, it writes the raw yuv values to a file (no padding), using the data provided by AVFrame after we successfully decoded a frame. To be more specific, I write out arrays AVFrame->data[0], AVFrame->data[1] and AVFrame->data[2] to a file, i.e. I simply append Y values, then U values, then V values to a file. The file turns out to be of yuv422p format.

  When I convert the same original video to a raw yuv format using the ffmpeg(same version of ffmpeg) command line tool, the two yuv files are the same in size, but differ in content.

  FYI, I am able to play both of the yuv files using the yuv player, and they look identical as well.

  Here is the exact command I run to convert the original video to a yuv video using ffmpeg command line tool

   ~/bin/ffmpeg -i super-short-video.h264 -c:v rawvideo -pix_fmt yuv422p  "super-short-video-yuv422p.yuv"

  What causes this difference in bytes and can it be fixed ? Is there perhaps another way of converting the original video to a yuv using the ffmpeg tool but maybe I need to use different settings ?

  Ffmpeg output when I convert to a yuv format :

  ffmpeg version N-80002-g5afecff Copyright (c) 2000-2016 the FFmpeg developers
  
    built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04.1)
  
    configuration: --prefix=/home/me/ffmpeg_build --pkg-config-flags=--static --extra-cflags=-I/home/me/ffmpeg_build/include --extra-ldflags=-L/home/me/ffmpeg_build/lib --bindir=/home/me/bin --enable-gpl --enable-libass --enable-libfdk-aac --enable-libfreetype --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-nonfree --extra-cflags=-pg --extra-ldflags=-pg --disable-stripping
  
    libavutil      55. 24.100 / 55. 24.100
  
    libavcodec     57. 42.100 / 57. 42.100
  
    libavformat    57. 36.100 / 57. 36.100
  
    libavdevice    57.  0.101 / 57.  0.101
  
    libavfilter     6. 45.100 /  6. 45.100
  
    libswscale      4.  1.100 /  4.  1.100
  
    libswresample   2.  0.101 /  2.  0.101
  
    libpostproc    54.  0.100 / 54.  0.100
  
  Input #0, h264, from 'super-short-video.h264':
  
    Duration: N/A, bitrate: N/A
  
      Stream #0:0: Video: h264 (High), yuv420p, 1280x720, 25 fps, 25 tbr, 1200k tbn
  
  [rawvideo @ 0x24f6fc0] Using AVStream.codec to pass codec parameters to muxers is deprecated, use AVStream.codecpar instead.
  
  Output #0, rawvideo, to 'super-short-video-yuv422p.yuv':
  
    Metadata:
  
      encoder         : Lavf57.36.100
  
      Stream #0:0: Video: rawvideo (Y42B / 0x42323459), yuv422p, 1280x720, q=2-31, 200 kb/s, 25 fps, 25 tbn
  
      Metadata:
  
        encoder         : Lavc57.42.100 rawvideo
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (h264 (native) -> rawvideo (native))
  
  Press [q] to stop, [?] for help
  
  frame=   50 fps=0.0 q=-0.0 Lsize=   90000kB time=00:00:02.00 bitrate=368640.0kbits/s speed=11.3x    
  
  video:90000kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.000000%