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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 - FFV1 frame encoding crashes on cleaning up

  21 mai 2016, par Yan

  I’m trying to implement a frame encoding functionality using the ffmpeg c-api. I am receiving frames from a camera which are in the Gray16le format. I want to convert encode them using the ffv1 encoder and copy the resulting frame into the variable "data". This is the code that I got so far. It seems to be working in a sense that it doesn’t crash until the part where I am freeing up my variables.

  /* Video compression variables///////////////////////////////////*/
  
  struct timeval stop, start;
  
  
  
  AVCodec *codec;
  
  AVCodecContext *context= NULL;
  
  const AVPixFmtDescriptor *avPixDesc = NULL; // used to get bits per pixel
  
  int ret, got_output;
  
  int bufferSize = 0; // Size of encoded image frame in bytes
  
  //uint8_t* outBuffer;
  
  AVFrame *inFrame; //
  
  AVPacket pkt;
  
  Data* data;
  
  /* Video compression ///////////////////////////////////*/
  
  
  
  Frame* frame;
  
  /////////////////////////////////////////////////////////////////////////
  
  // start frame compression - current codec is ffv1
  
  //////////////////////////////////////////////////////////////////////////
  
  
  
  gettimeofday(&start, NULL); // get current time
  
  avcodec_register_all(); // register all the codecs
  
  codec = avcodec_find_encoder(AV_CODEC_ID_FFV1); // find the ffv1 encoder
  
  if (!codec) {
  
      fprintf(stderr, "Codec not found\n");
  
      exit(1);
  
  }
  
  
  
  context = avcodec_alloc_context3(codec);
  
  if (!context) {
  
      fprintf(stderr, "Could not allocate video codec context\n");
  
      exit(1);
  
  }
  
  
  
  frame = getFrame(); // get frame so we can set context params
  
  
  
  /* put sample parameters */
  
  context->bit_rate = 400000; // from example, half might also work
  
  /* resolution must be a multiple of two */
  
  context->width = frame->size[0];
  
  context->height = frame->size[1];
  
  /* frames per second */
  
  context->time_base = (AVRational){1,22}; // 22 fps
  
  
  
  context->gop_size = 1; // typical for ffv1 codec
  
  context->max_b_frames = 1; // set to 1 for now, the higher the b-frames count, the higher the needed ressources
  
  context->pix_fmt = AV_PIX_FMT_GRAY16LE ; // same as source, Y , 16bpp, little-endian, 12 of the 16 pixels are used
  
  
  
  /* open it */
  
  if (avcodec_open2(context, codec, NULL) < 0) {
  
          fprintf(stderr, "Could not open codec\n");
  
          exit(1);
  
  }
  
  
  
  inFrame = av_frame_alloc();
  
  if(!inFrame)
  
  {
  
      printf("Could not allocate video frame\n! Exciting..");
  
      exit(1);
  
  }
  
  
  
  // allocate image in inFrame
  
  ret = av_image_alloc(inFrame->data, inFrame->linesize, context->width, context->height, context->pix_fmt, 16);
  
  if(ret<0)
  
  {
  
      printf("Error allocating image of inFrame! Exiting..\n");
  
      exit(1);
  
  }
  
  
  
  // copy data of frame of type Frame* into frame of type AVFrame* so we can use ffmpeg to encode it
  
  int picFill = avpicture_fill((AVPicture*)inFrame, (uint8_t*)frame->image, context->pix_fmt, context->width, context->height);
  
  
  
  if(picFill < 0)
  
  {
  
      printf("Error filling inFrame with frame->image! Exiting..\n");
  
      exit(1);
  
  }
  
  else
  
  {
  
      printf("Successfully filled inFrame with frame->image..\n");
  
      printf("Size of bytes filled:  %d", picFill);
  
  }
  
  
  
  inFrame->width = context->width;
  
  inFrame->height = context->height;
  
  inFrame->format = context->pix_fmt;
  
  
  
  if(frame->image[0] == NULL)
  
  {
  
          printf("Error! frame->image[0] == NULL.. Exiting..\n");
  
          exit(1);
  
  }
  
  
  
  fflush(stdout);
  
  int i=0;
  
  
  
  // start encoding
  
  while(!got_output) // while we didn't get a complete package
  
  {
  
      /* Start encoding the given frame */
  
      av_init_packet(&pkt);
  
      pkt.data = NULL;    // packet data will be allocated by the encoder
  
      pkt.size = 0;
  
  
  
      i++;
  
  
  
      /* encode the image */
  
      ret = avcodec_encode_video2(context, &pkt, inFrame, &got_output);
  
      if (ret < 0) {
  
              fprintf(stderr, "Error encoding frame\n");
  
              exit(1);
  
      }
  
  
  
      inFrame->pts = i;
  
  
  
      if(got_output)
  
      {
  
          printf("Got a valid package after %d frames..\n", i);
  
          // encoding of frame done, adapt "data"-field accordingly
  
          avPixDesc = av_pix_fmt_desc_get(context->pix_fmt); // Get pixelFormat descriptor
  
          bufferSize = av_image_get_buffer_size(context->pix_fmt, inFrame->width, inFrame->height,16);
  
          if(bufferSize <= 0)
  
          {
  
              printf("Error! Buffersize of encoded frame is <= 0, exciting...\n");
  
          }
  
          else
  
          {
  
              printf("Buffersize determined to be %d\n", bufferSize);
  
          }
  
  
  
          data->m_size[0] = inFrame->width;
  
          data->m_size[1] = inFrame->height;
  
          data->m_bytesPerPixel = av_get_bits_per_pixel(avPixDesc)/8;
  
  
  
          if (0 != av_get_bits_per_pixel(avPixDesc) % 8)
  
                  data->m_bytesPerPixel += 1;
  
  
  
          printf("Buffersize is: %d, should be %d\n", bufferSize, inFrame->width * inFrame->height * data->m_bytesPerPixel);
  
          data->m_image = malloc(bufferSize);
  
          printf("copying data into final variable...\n");
  
  
  
          memcpy(data->m_image, pkt.data, bufferSize); // copy data from ffmpeg frame
  
          printf("copying of data done\n");
  
  
  
          printf("Unrefing packet..\n");
  
          av_packet_unref(&pkt);
  
          printf("Unrefing packet done..\n");
  
      }
  
      else
  
      {
  
          printf("Didnt get package, so we get and encode next frame..\n");
  
          frame = getFrame(); // get next frame             
  
  
  
          picFill = avpicture_fill((AVPicture*)inFrame, (uint8_t*)frame->image, context->pix_fmt, context->width, context->height);
  
          if(!picFill)
  
          {
  
              printf("Error filling frame with data!!..\n");
  
              exit(1);
  
          }
  
          else
  
          {
  
              printf("Size required to store received frame in AVFrame in bytes: %d", picFill);
  
          }
  
      }
  
  }
  
  
  
  printf("\nDone with encoding.. cleaning up..\n");
  
  printf("Closing context...\n");
  
  avcodec_close(context);
  
  printf("Closing context done...\n");
  
  printf("Freeing context...\n");
  
  av_free(context);
  
  printf("Freeing context done...\n");
  
  if(inFrame->data[0] != NULL)
  
  {
  
      printf("avfreep() pointer to FFMPEG frame data...\n");
  
      av_freep(&inFrame->data[0]);
  
      printf("Freeing pointer to FFMPEG frame data done...\n");
  
  }
  
  else
  
  {
  
      printf("infRame->data[0] was not deleted because it was NULL\n");
  
  }
  
  
  
  printf("Freeing frame...\n");
  
  av_frame_free(&inFrame);
  
  printf("Freeing inFrame done...\n");
  
  printf("Compression of frame done...\n");
  
  gettimeofday(&stop, NULL);
  
  printf("took %lu ms\n", (stop.tv_usec - start.tv_usec) / 1000);

  This is the output that I am getting when I run the program :

  [ffv1 @ 0x75101970] bits_per_raw_sample > 8, forcing range coder
  
  Successfully filled inFrame with frame->image..
  
  Size of bytes filled:  1377792Got a valid package after 1 frames..
  
  Buffersize determined to be 1377792
  
  Buffersize is: 1377792, should be 1377792
  
  copying data into final variable...
  
  copying of data done
  
  Unrefing packet..
  
  Unrefing packet done..
  
  
  
  Done with encoding.. cleaning up..
  
  Closing context...
  
  Closing context done...
  
  Freeing context...
  
  Freeing context done...
  
  avfreep() pointer to FFMPEG frame data...
  
  *** Error in `./encoding': free(): invalid pointer: 0x74a66428 ***
  
  Aborted

  The error seems to occur when calling the av_freep() function. If you could point me in the right direction, it would be greatly appreciated ! This is my first time working with the ffmpeg api and I feel that I am not so close to my goal, though I spent quite some time looking for the error already..

  Best regards !

• Streaming video (C# using FFmpeg AutoGen) sends multiple data requests

  14 juillet 2016, par williamtroup

  I’ve written a video generator that rights a video in h264 format (mp4). When I stream the video from my azure service, i’m seeing the following network traffic :

  

  The AVCodecContext layout I’m using is as follows :

  AVCodec* videoCodec = ffmpeg.avcodec_find_encoder(AVCodecID.AV_CODEC_ID_H264)
  
  AVCodecContext* videoCodecContext = ffmpeg.avcodec_alloc_context3(videoCodec);
  
  videoCodecContext->bit_rate = 400000;
  
  videoCodecContext->width = 1280;
  
  videoCodecContext->height = 720;
  
  videoCodecContext->gop_size = 12;
  
  videoCodecContext->max_b_frames = 1;
  
  videoCodecContext->pix_fmt = videoCodec->pix_fmts[0];
  
  videoCodecContext->codec_id = videoCodec->id;
  
  videoCodecContext->codec_type = videoCodec->type;
  
  videoCodecContext->time_base = new AVRational
  
  {
  
      num = 1,
  
      den = 30
  
  };
  
  
  
  ffmpeg.av_opt_set(videoCodecContext->priv_data, "preset", "ultrafast");

  I’m also tried setting the "movflags" option for avformat_write_header() via an AVDictionary, but then av_write_trailer() returns -2, cause the file to not finish writing.

  I cannot figure out how to solve this problem. Videos generating using Windows Movie Maker stream perfectly.

  I know this has something to do with mdat and mov positions.

  Also, this appears to only happening in Google Chrome.