Recherche avancée

Sur d’autres sites (10295)

• FFmpeg : avcodec_encode_video() and JPEG images

  2 février 2012, par user105909

  I'm trying to encode a series of .jpg files into a video using the ffmpeg library, and I can't seem to get the frames to encode. (I have to use the ffmpeg library, and using ffmpeg from a command line is not an option in my case.)

  Except for the part where I'm trying to open JPG files as AVFrames, my code is more or less the same thing as found in api-example.c from the ffmpeg library. When I populate the frames as the example does, everything works as expected. In the code below, I fail to encode any frames. Obviously the trouble is related to how I'm opening the JPG files, but I can't figure out what.

  I'm opening the image like this :

  AVFrame* open_image(const char* imageFileName, int width, int height, long * bufSize)
  
  {
  
      AVFormatContext *pFormatCtx;
  
  
  
      if(av_open_input_file(&pFormatCtx, imageFileName, NULL, 0, NULL)!=0)
  
      {
  
          printf("Can't open image file '%s'\n", imageFileName);
  
          return NULL;
  
      }       
  
  
  
      AVCodecContext *pCodecCtx;
  
  
  
      pCodecCtx = pFormatCtx->streams[0]->codec;
  
      pCodecCtx->width = width;
  
      pCodecCtx->height = height;
  
      pCodecCtx->pix_fmt = PIX_FMT_YUV420P;
  
  
  
      // Find the decoder for the video stream
  
      AVCodec *pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
  
      if (!pCodec)
  
      {
  
          printf("Codec not found\n");
  
          return NULL;
  
      }
  
  
  
      // Open codec
  
      if(avcodec_open(pCodecCtx, pCodec)<0)
  
      {
  
          printf("Could not open codec\n");
  
          return NULL;
  
      }
  
  
  
      AVFrame *pFrame = avcodec_alloc_frame();
  
      if (!pFrame)
  
      {
  
          LOGV(TAG, "Can't allocate memory for AVFrame\n");
  
          return NULL;
  
      }
  
  
  
      int frameFinished;
  
      int numBytes;
  
  
  
      // Determine required buffer size and allocate buffer
  
      numBytes = avpicture_get_size(PIX_FMT_YUVJ420P, pCodecCtx->width, pCodecCtx->height);
  
  
  
      // ***
  
      *bufSize = numBytes;
  
      // ***
  
  
  
      uint8_t *buffer = (uint8_t *) av_malloc(numBytes * sizeof(uint8_t));
  
  
  
      avpicture_fill((AVPicture *) pFrame, buffer, PIX_FMT_YUVJ420P, pCodecCtx->width, pCodecCtx->height);
  
  
  
      // Read frame
  
  
  
      AVPacket packet;
  
  
  
      int framesNumber = 0;
  
      while (av_read_frame(pFormatCtx, &packet) >= 0)
  
      {
  
          if(packet.stream_index != 0)
  
              continue;
  
  
  
          int ret = avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);
  
          if (ret > 0)
  
          {
  
              sprintf(buf, "Frame is decoded, size %d", ret);
  
              LOGV(TAG, buf);
  
              pFrame->quality = 4;
  
              return pFrame;
  
          }
  
          else {
  
              // printf("Error [%d] while decoding frame: %s\n", ret, strerror(AVERROR(ret)));
  
              sprintf(buf, "Error %d decoding frame: %s", ret, strerror(AVERROR(ret)));
  
              LOGV(TAG, buf);
  
          }
  
      }
  
  }

  ...and attempting to encode them like this :

  DIR * dir = opendir(path);
  
  int i = 0;
  
  
  
  if (dir != NULL) {
  
  
  
      for(struct dirent *ent = readdir(dir); ent != NULL; ent = readdir(dir)) {
  
          fflush(stdout);
  
  
  
          printf("%s/%s", path, ent->d_name);
  
          LOGV(TAG, filename);
  
  
  
          // If not a jpg file, pass it over
  
          const char * ext = strrchr(filename, '.');
  
          if((!ext) || (strcmp(ext, ".jpg"))) {
  
              continue;
  
          }
  
  
  
          /*** NOTE: Is this where I've gone wrong? Bufsize is set in open_image based on av_picture_size() */
  
          long bufSize = 0L;
  
          AVFrame * frame = open_image(filename, width, height, &bufSize);
  
          if(frame) {
  
              // This is what it needs to do, and it does not work.
  
              // Causes:
  
              // Wrong format?
  
              // Wrong buffer size?
  
              uint8_t * picBuf = (uint8_t *)malloc(bufSize);
  
  
  
              out_size = avcodec_encode_video(c, picBuf, bufSize, frame);
  
  
  
              printf("encoding frame %3d (size=%5d)\n", i++, out_size);
  
              /** On the first image, out_size is 0. On the next, it's -1, and fails. */
  
  
  
              if(out_size < 0) {
  
                  printf("Error encoding frame");
  
                  return -6;
  
              }
  
  
  
              fwrite(picBuf, 1, bufSize, f);
  
  
  
              free(picBuf);
  
              av_free(frame);
  
          }
  
          else {
  
              printf("Couldn't open image");
  
              return -5;
  
          }
  
      }
  
  
  
      closedir(dir);
  
  } 
  
  else {
  
      printf("Couldn't open directory %s\n", path);
  
      return -4;
  
  }

  Could someone point me in the right direction ?

• Anomalie #2693 (Nouveau) : Page des statistiques

  8 mai 2012, par jluc -

  Testée sur spip-contrib, la page statistiques ?exec=stats_visites présente quelques petits problèmes : Le tableau de liens dans la 2eme partie de la page concentre une bonne part de mes remarques : Le titre "Afficher les visites pour les articles les plus populaires et pour les derniers articles (...)

• How to generate gif from avi using ffmpeg ?

  19 décembre 2012, par Marconi

  I'm trying to extract a part of a video into an animated gif using the following command :

  ffmpeg -i video.avi -t 5 out.gif

  It generates an animated gif but the quality is insane. However when I generate gif image using :

  ffmpeg -i video.avi -t 10 out%d.gif

  It generates acceptable quality of gif images. How can i generate animated gif using the first command but the same quality as the second command ?