ffmpeg valgrind test case

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>

#define CONTAINER_FORMAT "matroska"
#define VIDEO_FILENAME   "test.mkv"
#define WIDTH            640
#define HEIGHT           480
#define PIX_FMT_IN       PIX_FMT_YUV420P
#define PIX_FMT_OUT      PIX_FMT_RGB24

int
main(void)
{
  AVInputFormat   *format;
  AVFormatContext *format_ctx;
  AVCodec         *codec, *image_codec;
  AVCodecContext  *codec_ctx, *image_codec_ctx;

  avcodec_register_all();
  av_register_all();

  format = av_find_input_format(CONTAINER_FORMAT);
  if (format == NULL) return 1;

  format_ctx = avformat_alloc_context();
  if (avformat_open_input(&format_ctx, VIDEO_FILENAME, format, NULL) != 0) return 1;

  codec_ctx = format_ctx->streams[0]->codec;

  codec = avcodec_find_decoder(codec_ctx->codec_id);
  if (codec == NULL) return 1;

  if (codec->capabilities & CODEC_CAP_TRUNCATED) {
    codec_ctx->flags |= CODEC_FLAG_TRUNCATED;
  }

  if (avcodec_open2(codec_ctx, codec, NULL) != 0) return 1;

  image_codec = avcodec_find_encoder(AV_CODEC_ID_PNG);
  if (image_codec == NULL) return 1;

  image_codec_ctx = avcodec_alloc_context3(image_codec);
  if (image_codec_ctx == NULL) return 1;
  image_codec_ctx->pix_fmt = AV_PIX_FMT_RGB24;
  image_codec_ctx->width   = WIDTH;
  image_codec_ctx->height  = HEIGHT;

  if (avcodec_open2(image_codec_ctx, image_codec, NULL) != 0) return 1;

  struct SwsContext *img_convert_ctx = sws_getContext(
    WIDTH, HEIGHT, PIX_FMT_IN,
    WIDTH, HEIGHT, PIX_FMT_OUT,
    SWS_FAST_BILINEAR, NULL, NULL, NULL
  );

  AVFrame *frame = avcodec_alloc_frame();

  int got_frame, got_packet;
  AVPacket packet;

  av_init_packet(&packet);
  packet.data = NULL;
  packet.size = 0;

  AVFrame *frame2 = avcodec_alloc_frame();
  int buf_size = avpicture_get_size(PIX_FMT_OUT, WIDTH, HEIGHT);
  uint8_t *buf = malloc(buf_size);
  avpicture_fill(
    (AVPicture *)frame2,
    buf,
    PIX_FMT_OUT,
    WIDTH, HEIGHT
  );

  while (av_read_frame(format_ctx, &packet) >= 0) {
    if (avcodec_decode_video2(codec_ctx, frame, &got_frame, &packet) < 0) return 1;

    if (got_frame) {
      sws_scale(
        img_convert_ctx, (const uint8_t * const *)frame->data, frame->linesize,
        0, HEIGHT,
        frame2->data, frame2->linesize
      );

      av_init_packet(&packet);
      packet.data = NULL;
      packet.size = 0;

      /* If this next block is commented out, valgrind shows no invalid reads
       * or use of uninitialized values.
       */
      if (avcodec_encode_video2(image_codec_ctx, &packet, frame2, &got_packet) < 0) return 1;
      printf("### packet size: %d\n", packet.size);
      if (got_packet) {
        int fd = open("frame.png", O_CREAT|O_WRONLY|O_TRUNC, 0600);
        write(fd, packet.data, packet.size);
        close(fd);
      }

      break; /* just process one frame */
    }
  }

  return 0;
}