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• Use imagick->pingImage to retrieve the image dimensions.

  14 octobre 2013, par blueimp

  Use imagick->pingImage to retrieve the image dimensions.
  Delegate to the get_image_size method to determine the image validity.
  

• 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 ?

• ffmpeg YUV to RGB distored color and position

  15 novembre 2012, par user1542140

  Sorry that I still cannot post images for my question since low reputation.

  I use the ffmpeg function to convert the decoded frame, from YUV to RGB24, but the color and resulted image is distorted seriously. Following is my code snip, the frame width and height is (176, 144)

  len = avcodec_decode_video2(c, picture, &got_picture, &avpkt);
  
      if (got_picture) {
  
              //...
  
  
  
      AVFrame *pFrameRGB = avcodec_alloc_frame();
  
      // Determine required buffer size and allocate buffer
  
      int numBytes=avpicture_get_size(PIX_FMT_RGB24, c->width, c->height);
  
      uint8_t *buffer=(uint8_t *)av_malloc(numBytes*sizeof(uint8_t));
  
      avpicture_fill((AVPicture *)pFrameRGB, buffer, PIX_FMT_RGB24, c->width, c->height);
  
  
  
      struct SwsContext *img_convert_ctx = sws_getContext(c->width, c->height, PIX_FMT_YUV420P, c->width, c->height, PIX_FMT_BGR24, SWS_BICUBIC, NULL, NULL, NULL);
  
      sws_scale(img_convert_ctx, picture->data, picture->linesize, 0, picture->height, pFrameRGB->data, pFrameRGB->linesize);
  
      sws_freeContext(img_convert_ctx);
  
      // Save the frame to disk
  
      if(++frame<=5)
  
          SaveFrame(pFrameRGB, c->width, c->height, frame);