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• why is streaming to an flv server with ffmpeg only showing black/blank video for clients ?

  6 septembre 2012, par rogerdpack

  When I stream to an flv server, like flash media server, using ffmpeg, like

   ffmpeg -i input -vcodec libx264 rtmp://hostname/streamname

  it turns out black. Why is that ?

• getting black and white image after encoding

  16 mai 2012, par user1310596

  I am trying to encode image using ffmpeg library and objective c. I am using following code but I am getting black and white image as the result. Is there something to do with pixel format(PIX_FMT) ? Please help me so that I can get colored image.

  av_register_all();
  
  avcodec_init();
  
  avcodec_register_all();
  
  avformat_alloc_context();
  
  
  
  AVCodec *codec;
  
  AVCodecContext *ctx= NULL;
  
  int out_size, size, outbuf_size;
  
  AVFrame *picture;
  
  uint8_t *outbuf;
  
  unsigned char *flvdata = malloc(sizeof(unsigned char) * 30);
  
  
  
  
  
  outbuf_size = 200000;
  
  outbuf = malloc(outbuf_size);
  
  
  
  
  
  printf("Video encoding\n");
  
  
  
  codec = avcodec_find_encoder(CODEC_ID_FLV1);
  
  if (!codec) {
  
          fprintf(stderr, "codec not found\n");
  
          exit(1);
  
  }
  
  
  
  ctx= avcodec_alloc_context();
  
  picture= avcodec_alloc_frame();
  
  
  
  
  
  ctx->width = 320;
  
  ctx->height = 240;
  
  ctx -> sample_rate = 11025;
  
  ctx -> time_base.den = 1000;
  
  ctx -> time_base.num = 23976;
  
  ctx -> codec_id = CODEC_ID_FLV1;
  
  ctx -> codec_type = CODEC_TYPE_VIDEO;
  
  ctx->pix_fmt = PIX_FMT_YUV420P;
  
  
  
  if (avcodec_open(ctx, codec) < 0) {
  
          fprintf(stderr, "could not open codec\n");
  
          exit(1);
  
  }
  
  
  
  outbuf_size = 100000;
  
  outbuf = malloc(outbuf_size);
  
  size = ctx->width * ctx->height;
  
  
  
  AVFrame* outpic = avcodec_alloc_frame();
  
  int nbytes = avpicture_get_size(PIX_FMT_YUV420P, ctx->width, ctx->height);
  
  
  
  uint8_t* outbuffer = (uint8_t*)av_malloc(nbytes);
  
  
  
  fflush(stdout);
  
  
  
  int numBytes = avpicture_get_size(PIX_FMT_YUV420P, ctx->width, ctx->height);
  
  
  
  UIImage *image = [UIImage imageNamed:[NSString stringWithFormat:@"0.jpg"]];
  
  CGImageRef newCgImage = [image CGImage];
  
  
  
  CGDataProviderRef dataProvider = CGImageGetDataProvider(newCgImage);
  
  CFDataRef bitmapData = CGDataProviderCopyData(dataProvider);
  
  long dataLength = CFDataGetLength(bitmapData);
  
  
  
  uint8_t *buffer = (uint8_t *)av_malloc(dataLength);
  
  buffer = (uint8_t *)CFDataGetBytePtr(bitmapData);
  
  
  
  for(int i = 0; i < dataLength; i++)
  
  {
  
          if((i + 1) % 16 == 1 && i != 1)
  
                  printf("\n");
  
          printf("%X\t",buffer[i]); // getting something different than the     actual hex value of the image
  
  }
  
  
  
  
  
  
  
  outpic -> pts = 0;        
  
  
  
  avpicture_fill((AVPicture*)picture, buffer, PIX_FMT_RGB8, ctx->width, ctx->height);
  
  
  
  avpicture_fill((AVPicture*)outpic, outbuffer, PIX_FMT_YUV420P, ctx->width, ctx->height);
  
  
  
  struct SwsContext* fooContext = sws_getContext(ctx->width, ctx->height, 
  
                                                         PIX_FMT_RGB8, 
  
                                                         ctx->width, ctx->height, 
  
                                                         PIX_FMT_YUV420P, 
  
                                                         SWS_FAST_BILINEAR, NULL, NULL, NULL);
  
  
  
  sws_scale(fooContext, picture->data, picture->linesize, 0, ctx->height, outpic->data, outpic->linesize);
  
  
  
  printf("abcdefghijklmnop");
  
  out_size = avcodec_encode_video(ctx, outbuf, outbuf_size, outpic);
  
  printf("\n\n out_size %d   outbuf_size %d",out_size,outbuf_size);

  Thanks in advance

• JavaCV - strange black screen when playing a file with FFmpegFrameGrabber

  17 mai 2012, par noncom

  I am using JavaCV and it's FFmpegFrameGrabber in my project. It loads and player files OK, when I launch the project from Eclipse, but shows either a black screen or a still 1st frame when I run a compiled project. Sometimes comming with this error :

  Input #0, avi, from 'C:/path/Start_Cut.avi':
  
  Duration: 00:00:20.03, start: 0.000000, bitrate: 26002 kb/s
  
  Stream #0.0: Video: mpeg4, yuv420p, 1920x1080, 30 tbr, 30 tbn, 30 tbc
  
  Cannot allocate memory. com.googlecode.javacv.FrameGrabber$Exception: Cannot initialize the conversion c ontext.
  
              at com.googlecode.javacv.FFmpegFrameGrabber.start(FFmpegFrameGrabber.jav a:280)

  and sometimes with

  [mpeg4 @ 6A95DF20] Invalid and inefficient vfw-avi packed B frames detected
  
  Input #0, avi, from 'C:/path/Start_Cut.avi':
  
    Duration: 00:00:20.03, start: 0.000000, bitrate: 26002 kb/s
  
      Stream #0.0: Video: mpeg4, yuv420p, 1920x1080 [PAR 1:1 DAR 16:9], 25 tbr, 30
  
   tbn, 25 tbc

  does anyone has a clue on this ?

  UPDATE :

  I have been able to narrow down the problem. For some reason, FFmpegFrameGrabber returns null upn calling the grab() method. Why does it work in Eclipse and does not work in standalone build ? All libraries are included and I suppose, it would come up with an error if they did not.