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• H264 decoding using ffmpeg

  14 juillet 2016, par Kindermann

  I’m trying to decode a video stream with ffmpeg library, that’s how I do it basically :

  void video_decode(const char *filename)
  
  {
  
      AVCodec *codec;
  
      AVCodecContext *c= NULL;
  
      int frame_count=0;
  
      FILE *f;
  
      AVFrame *frame;
  
      uint8_t inbuf[INBUF_SIZE + AV_INPUT_BUFFER_PADDING_SIZE];
  
      AVPacket avpkt;
  
      av_init_packet(&avpkt);
  
      memset(inbuf + INBUF_SIZE, 0, AV_INPUT_BUFFER_PADDING_SIZE);
  
      printf("Decoding video file...\n");
  
      /* find the h264 video decoder */
  
      codec = avcodec_find_decoder(AV_CODEC_ID_H264);
  
      c = avcodec_alloc_context3(codec);
  
      c->bit_rate = 400000;
  
      c->width = 1920;
  
      c->height = 1080;
  
  
  
      if (avcodec_open2(c, codec, NULL) < 0) {
  
          fprintf(stderr, "Could not open codec\n");
  
          exit(1);
  
      }
  
      frame = av_frame_alloc();
  
      for (;;) {
  
          avpkt.size = fread(inbuf, 1, INBUF_SIZE, f);         
  
      if (avpkt.size == 0)
  
              break;
  
          avpkt.data = inbuf;
  
          while(avpkt.size > 0){
  
  
  
          int len, got_frame;
  
              len = avcodec_decode_video2(c, frame, &got_frame, &avpkt);          
  
          if (len < 0) {
  
                  fprintf(stderr, "Errr while decding frame %d\n", frame_count);
  
                  exit (1);
  
              }
  
              if (got_frame) {
  
                  //Print out frame information..
  
          }
  
              if (avpkt.data) {
  
                  avpkt.size -= len;
  
                  avpkt.data += len;
  
              }
  
      }               
  
      }  
  
  }

  But I got the following outputs :

  Decoding video file...
  
  [h264 @ 0x303c040] decode_slice_header error
  
  [h264 @ 0x303c040] decode_slice_header error
  
  [h264 @ 0x303c040] decode_slice_header error
  
  [h264 @ 0x303c040] no frame!
  
  Errr while decding frame 0

  Obviously the initiation of codec was incomplete. Do you have experience with h264 api ? Any help would be appreciated.

• Libavcodec and QuickSync

  15 février 2016, par FrancescoBLT

  I’m attempting to encode in h264 format using libavcodec with and without QuickSync hardware acceleration. If I don’t use the hw acceleration is quite simple :

  ff_codec = avcodec_find_encoder(AV_CODEC_ID_H264) ;

  ff_cdctx = avcodec_alloc_context3(ff_codec) ;

  ff_cdctx->width = 1920;
  
  ff_cdctx->height = 1080;
  
  ff_cdctx->time_base.num = 1;
  
  ff_cdctx->time_base.den = 25;
  
  ff_cdctx->sample_aspect_ratio.num = 16;
  
  ff_cdctx->sample_aspect_ratio.den = 9;
  
  ff_cdctx->pix_fmt = AV_PIX_FMT_YUV420P;
  
  av_dict_set(&param,"profile","main",0);
  
  av_dict_set(&param,"preset","medium",0);
  
  av_dict_set(&param,"tune","film",0)<0);
  
  ff_cdctx->gop_size = 10;
  
  ff_cdctx->max_b_frames = 1;
  
  opres = avcodec_open2(ff_cdctx,ff_codec,&param);
  
  ff_frame = av_frame_alloc();
  
  ff_frame->format = ff_cdctx->pix_fmt;
  
  ff_frame->width  = ff_cdctx->width;
  
  ff_frame->height = ff_cdctx->height; 
  
  
  
  opres = av_image_alloc(ff_frame->data, ff_frame->linesize,ff_cdctx->width,ff_cdctx->height,ff_cdctx->pix_fmt, 32);
  
  ff_frame->linesize[0] = ff_cdctx->width;
  
  ff_frame->linesize[1] = ff_frame->linesize[2] = ff_cdctx->width>>1;
  
  
  
  ff_frame->sample_aspect_ratio.num = ff_cdctx->sample_aspect_ratio.num;
  
  ff_frame->sample_aspect_ratio.den = ff_cdctx->sample_aspect_ratio.den;
  
  av_init_packet(&pkt);
  
  enc_err = avcodec_encode_video2(ff_cdctx,&pkt,ff_frame,&got_pkt);  }

  And so on for all source frame. Problem arise when I attempt to use hardware
  acceleration. In this case I use :

  ff_codec = avcodec_find_encoder_by_name("h264_qsv") ;
  for gathering the codec. But when I attempt to open it, the result is "invalid parameter" :
  opres = avcodec_open2(ff_cdctx,ff_codec,&param) ;
  if(opres<0)
  
  if(av_strerror(opres,err_str,256)==0) OutputDebugStringA(err_str) ;
  return -6 ;
  
  Did anyone have attempted to use QuickSync from code ? In the examples there is only one file (qsvdec.c) and is for decoding, not for encoding.
  regards

• What is the commmand line to record destop screen with watermark using ffmpeg ?

  11 septembre 2020, par Yong Ju

  I tried to record screen using ffmpeg commmand line. So, I have complete it using this commmand.&#xA;ffmpeg.exe -rtbufsize 1500M -f -y -rtbufsize 100M -f gdigrab -t 00:02:00 -framerate 30 0 0 -probesize 10M 1920 1080 -draw_mouse 1 -i desktop -c:v libx264 -r 30 -preset ultrafast -tune zerolatency -crf 30 -pix_fmt yuv420p output.avi".

  &#xA;

  Now, I want to add watermark while recording video.&#xA;If you have good experience this field, Please give me good advice.&#xA;Thanks for your attention.&#xA;Sincerely.

  &#xA;