get_and_display_frames.c

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

#include <SDL.h>
#include <SDL_thread.h>

#ifdef __MINGW32__
#undef main /* Prevents SDL from overriding main() */
#endif

#include <stdio.h>

int main(int argc, char *argv[]) {
  AVFormatContext *pFormatCtx = NULL;
  int             i, videoStream;
  AVCodecContext  *pCodecCtx = NULL;
  AVCodec         *pCodec = NULL;
  AVFrame         *pFrame = NULL; 
  AVPacket        packet;
  int             frameFinished;
  //float           aspect_ratio;

  AVDictionary    *optionsDict = NULL;
  struct SwsContext *sws_ctx = NULL;

  SDL_Overlay     *bmp = NULL;
  SDL_Surface     *screen = NULL;
  SDL_Rect        rect;
  SDL_Event       event;

  if(argc < 2) {
    fprintf(stderr, "Usage: test <file>\n");
    exit(1);
  }
  // Register all formats and codecs
  av_register_all();
  
  if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)) {
    fprintf(stderr, "Could not initialize SDL - %s\n", SDL_GetError());
    exit(1);
  }

  // Open video file
  if(avformat_open_input(&pFormatCtx, argv[1], NULL, NULL)!=0)
    return -1; // Couldn't open file
  
  // Retrieve stream information
  if(avformat_find_stream_info(pFormatCtx, NULL)<0)
    return -1; // Couldn't find stream information
  
  // Dump information about file onto standard error
  av_dump_format(pFormatCtx, 0, argv[1], 0);
  
  // Find the first video stream
  videoStream=-1;
  for(i=0; i<pFormatCtx->nb_streams; i++)
    if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO) {
      videoStream=i;
      break;
    }
  if(videoStream==-1)
    return -1; // Didn't find a video stream
  
  // Get a pointer to the codec context for the video stream
  pCodecCtx=pFormatCtx->streams[videoStream]->codec;
  
  // Find the decoder for the video stream
  pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
  if(pCodec==NULL) {
    fprintf(stderr, "Unsupported codec!\n");
    return -1; // Codec not found
  }
  
  // Open codec
  if(avcodec_open2(pCodecCtx, pCodec, &optionsDict)<0)
    return -1; // Could not open codec
  
  // Allocate video frame
  pFrame=av_frame_alloc();

  // Make a screen to put our video
#ifndef __DARWIN__
        screen = SDL_SetVideoMode(pCodecCtx->width, pCodecCtx->height, 0, 0);
#else
        screen = SDL_SetVideoMode(pCodecCtx->width, pCodecCtx->height, 24, 0);
#endif
  if(!screen) {
    fprintf(stderr, "SDL: could not set video mode - exiting\n");
    exit(1);
  }
  
  // Allocate a place to put our YUV image on that screen
  bmp = SDL_CreateYUVOverlay(pCodecCtx->width,
				 pCodecCtx->height,
				 SDL_YV12_OVERLAY,
				 screen);
  
  sws_ctx =
    sws_getContext
    (
        pCodecCtx->width,
        pCodecCtx->height,
        pCodecCtx->pix_fmt,
        pCodecCtx->width,
        pCodecCtx->height,
        PIX_FMT_YUV420P,
        SWS_BILINEAR,
        NULL,
        NULL,
        NULL
    );

  // Read frames and save first five frames to disk
  i=0;
  while(av_read_frame(pFormatCtx, &packet)>=0) {
    // Is this a packet from the video stream?
    if(packet.stream_index==videoStream) {
      // Decode video frame
      avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, 
			   &packet);
      
      // Did we get a video frame?
      if(frameFinished) {
	SDL_LockYUVOverlay(bmp);

	AVPicture pict;
	pict.data[0] = bmp->pixels[0];
	pict.data[1] = bmp->pixels[2];
	pict.data[2] = bmp->pixels[1];

	pict.linesize[0] = bmp->pitches[0];
	pict.linesize[1] = bmp->pitches[2];
	pict.linesize[2] = bmp->pitches[1];

	// Convert the image into YUV format that SDL uses
    sws_scale
    (
        sws_ctx, 
        (uint8_t const * const *)pFrame->data, 
        pFrame->linesize, 
        0,
        pCodecCtx->height,
        pict.data,
        pict.linesize
    );
	
	SDL_UnlockYUVOverlay(bmp);
	
	rect.x = 0;
	rect.y = 0;
	rect.w = pCodecCtx->width;
	rect.h = pCodecCtx->height;
	SDL_DisplayYUVOverlay(bmp, &rect);
      
      }
    }
    
    // Free the packet that was allocated by av_read_frame
    av_free_packet(&packet);
    SDL_PollEvent(&event);
    switch(event.type) {
    case SDL_QUIT:
      SDL_Quit();
      exit(0);
      break;
    default:
      break;
    }

  }
  
  // Free the YUV frame
  av_free(pFrame);
  
  // Close the codec
  avcodec_close(pCodecCtx);
  
  // Close the video file
  avformat_close_input(&pFormatCtx);
  
  return 0;
}