Recherche avancée

Sur d’autres sites (15682)

• Files created with a direct stream copy using FFmpeg's libavformat API play back too fast at 3600 fps

  2 octobre 2013, par Chris Ballinger

  I am working on a libavformat API wrapper that converts MP4 files with H.264 and AAC to MPEG-TS segments suitable for streaming. I am just doing a simple stream copy without re-encoding, but the files I produce play the video back at 3600 fps instead of 24 fps.

  Here are some outputs from ffprobe https://gist.github.com/chrisballinger/6733678, the broken file is below :

  r_frame_rate=1/1
  
  avg_frame_rate=0/0
  
  time_base=1/90000
  
  start_pts=0
  
  start_time=0.000000
  
  duration_ts=2999
  
  duration=0.033322

  The same input file manually sent through ffmpeg has proper timestamp information :

  r_frame_rate=24/1
  
  avg_frame_rate=0/0
  
  time_base=1/90000
  
  start_pts=126000
  
  start_time=1.400000
  
  duration_ts=449850
  
  duration=4.998333

  I believe the problem lies somewhere in my setup of libavformat here : https://github.com/OpenWatch/FFmpegWrapper/blob/master/FFmpegWrapper/FFmpegWrapper.m#L349 where I repurposed a bunch of code from ffmpeg.c that was required for the direct stream copy.

  Since 3600 seems like a "magic number" (60*60), it could be as simple as me not setting the time scale properly, but I can't figure out where my code diverges from ffmpeg/avconv itself.

  Similar question here, but I don't think they got as far as I did : Muxing a H.264 Annex B & AAC stream using libavformat with vcopy/acopy

• Extremely high bit rate when encoding video with libavcodec

  10 janvier 2014, par niculare

  I am trying to capture the camera output and make a video using libavcodec. As an example on how to accomplish this i have used ffmpeg muxing example.

  The problem is that a 4 seconds video has a size of 15mb and a bitrate of 30000 kb/s, although I have set the bitrate on AVCodecContext to 400000 (I consider this value is in bits / sec, not kb/s).

  I have also tried to record the video using ffmpeg from command line and it has a bitrate of 700 kb/s.

  Does anybody have an idea why the bitrate is not preserved and thus the resulting file is very large ? The code I have used to initialize the codec context is below :

  initialization part :

  avformat_alloc_output_context2(&m_formatContext, NULL, NULL, filename);
  
  outputFormat = m_formatContext->oformat;
  
  
  
  codec = avcodec_find_encoder(outputFormat->video_codec);
  
  
  
  m_videoStream = avformat_new_stream(m_formatContext, codec);
  
  
  
  m_videoStream->id = m_formatContext->nb_streams - 1;
  
  
  
  codecContext = m_videoStream->codec;
  
  
  
  codecContext->codec_id = outputFormat->video_codec;
  
  
  
  codecContext->width = m_videoResolution.width();
  
  codecContext->height = m_videoResolution.height();
  
  
  
  int m_bitRate = 400000;
  
  codecContext->bit_rate = m_bitRate;
  
  codecContext->rc_min_rate = m_bitRate;
  
  codecContext->rc_max_rate = m_bitRate;
  
  codecContext->bit_rate_tolerance = 0;
  
  
  
  codecContext->time_base.den = 20;
  
  codecContext->time_base.num = 1;
  
  
  
  codecContext->pix_fmt = AV_PIX_FMT_YUV422P;
  
  
  
  if (m_formatContext->oformat->flags & AVFMT_GLOBALHEADER)
  
      codecContext->flags |= CODEC_FLAG_GLOBAL_HEADER;
  
  /* open it */
  
  ret = avcodec_open2(codecContext, codec, NULL);
  
  
  
  avFrame = avcodec_alloc_frame();
  
  
  
  ret = avpicture_alloc(&avPicture, codecContext->pix_fmt, codecContext->width, codecContext->height);
  
  
  
  *((AVPicture *)avFrame) = avPicture;
  
  
  
  av_dump_format(m_formatContext, 0, filename, 1);
  
  
  
  if (!(outputFormat->flags & AVFMT_NOFILE)) {
  
      ret = avio_open(&m_formatContext->pb, filename, AVIO_FLAG_WRITE);
  
  }
  
  
  
  ret = avformat_write_header(m_formatContext, NULL);
  
  
  
  if (avFrame)
  
      avFrame->pts = 0;

• Bitmap images to WEBM video encoding

  21 novembre 2013, par Ankush

  I am trying to encode bitmap images to webm video,but generated video is not playable
  Here is code I am using,code works fine for H624.
  While encoding console windows shows : [libvpx @ 009b2f60] v1.2.0
  there is no webm string in produced video file. Any clue ? ( I am newbie for FFMPEG API )

  void create_from_bmp()
  
  {
  
  CFile file[5];  
  
  BYTE *szTxt[5];  
  
  
  
  int nWidth = 0;  
  
  int nHeight= 0;  
  
  
  
  int nDataLen=0;  
  
  
  
  int nLen;  
  
  
  
  CString csFileName;  
  
  for (int fileI = 1; fileI <= 5; fileI ++)  
  
  {
  
    csFileName.Format("e:\\pics\\%d.bmp",fileI);  
  
    file[fileI - 1].Open(csFileName,CFile::modeRead | CFile::typeBinary);  
  
    nLen = file[fileI - 1].GetLength();  
  
  
  
    szTxt[fileI -1] = new BYTE[nLen];  
  
    file[fileI - 1].Read(szTxt[fileI - 1], nLen);  
  
    file[fileI - 1].Close();  
  
  
  
    //BMP bmi;//BITMAPINFO bmi;  
  
    //int nHeadLen = sizeof(BMP);  
  
    BITMAPFILEHEADER bmpFHeader;  
  
    BITMAPINFOHEADER bmpIHeader;  
  
    memcpy(&bmpFHeader,szTxt[fileI -1],sizeof(BITMAPFILEHEADER));  
  
  
  
    int nHeadLen = bmpFHeader.bfOffBits - sizeof(BITMAPFILEHEADER);  
  
    memcpy(&bmpIHeader,szTxt[fileI - 1]+sizeof(BITMAPFILEHEADER),nHeadLen);  
  
  
  
    nWidth = bmpIHeader.biWidth;// 464;// bmi.bmpInfo.bmiHeader.biWidth;// ;  
  
    nHeight = bmpIHeader.biHeight;//362;// bmi.bmpInfo.bmiHeader.biHeight;// ;  
  
  
  
    szTxt[fileI - 1] += bmpFHeader.bfOffBits;  
  
    nDataLen = nLen-bmpFHeader.bfOffBits;  
  
  }  
  
  
  
  av_register_all();  
  
  avcodec_register_all();  
  
  AVFrame *m_pRGBFrame =  new AVFrame[1];  //RGB    
  
  AVFrame *m_pYUVFrame = new AVFrame[1];;  //YUV
  
  AVCodecContext *c= NULL;  
  
  AVCodecContext *in_c= NULL;  
  
  AVCodec *pCodecH264;
  
  uint8_t * yuv_buff;//  
  
  
  
  pCodecH264 = avcodec_find_encoder(CODEC_ID_VP8);  
  
  if(!pCodecH264)  
  
  {  
  
    fprintf(stderr, "h264 codec not found\n");  
  
    exit(1);  
  
  }  
  
  
  
  c= avcodec_alloc_context3(pCodecH264);  
  
  c->bit_rate = 3000000;// put sample parameters   
  
  c->width =nWidth;//   
  
  c->height = nHeight;//  
  
  
  
  // frames per second   
  
  AVRational rate;  
  
  rate.num = 1;  
  
  rate.den = 5;  //5 frames per sec
  
  c->time_base= rate;//(AVRational){1,25};  
  
  c->gop_size = 10; // emit one intra frame every ten frames   //emit one iframe per sec
  
  c->max_b_frames=0;  //
  
  c->thread_count = 1;  
  
  c->pix_fmt = PIX_FMT_YUV420P;//PIX_FMT_RGB24;  
  
  c->codec_id=CODEC_ID_VP8;
  
  
  
  //av_opt_set(c->priv_data, /*"preset"*/"libvpx-1080p.ffpreset", /*"slow"*/NULL, 0);  
  
  if(avcodec_open2(c,pCodecH264,NULL)<0)  
  
    printf("Cant open codec");
  
  
  
  int size = c->width * c->height;  
  
  
  
  yuv_buff = (uint8_t *) malloc((size * 3) / 2); // size for YUV 420    
  
  
  
  uint8_t * rgb_buff = new uint8_t[nDataLen];  
  
  
  
  int outbuf_size=400000;  
  
  uint8_t * outbuf= (uint8_t*)malloc(outbuf_size);   
  
  int u_size = 0;  
  
  FILE *f=NULL;   
  
  char * filename = "e:\\pics\\myData.h264";  
  
  f = fopen(filename, "wb");  
  
  if (!f)  
  
  {  
  
    printf( "could not open %s\n", filename);  
  
    exit(1);  
  
  }  
  
  
  
  //SwsContext  
  
  SwsContext * scxt = sws_getContext(c->width,c->height,PIX_FMT_BGR24,c->width,c->height,PIX_FMT_YUV420P,SWS_POINT,NULL,NULL,NULL);  
  
  
  
  AVPacket avpkt;  
  
  
  
  //AVFrame *pTFrame=new AVFrame  
  
  for (int i=0;i<60;++i)  
  
  {  
  
    //AVFrame *m_pYUVFrame = new AVFrame[1];  
  
  
  
    int index = (i / 5) % 5;  
  
    memcpy(rgb_buff,szTxt[index],nDataLen);  
  
  
  
    avpicture_fill((AVPicture*)m_pRGBFrame, (uint8_t*)rgb_buff, PIX_FMT_RGB24, nWidth, nHeight);  
  
  
  
    avpicture_fill((AVPicture*)m_pYUVFrame, (uint8_t*)yuv_buff, PIX_FMT_YUV420P, nWidth, nHeight);  
  
  
  
    m_pRGBFrame->data[0]  += m_pRGBFrame->linesize[0] * (nHeight - 1);  
  
    m_pRGBFrame->linesize[0] *= -1;                     
  
    m_pRGBFrame->data[1]  += m_pRGBFrame->linesize[1] * (nHeight / 2 - 1);  
  
    m_pRGBFrame->linesize[1] *= -1;  
  
    m_pRGBFrame->data[2]  += m_pRGBFrame->linesize[2] * (nHeight / 2 - 1);  
  
    m_pRGBFrame->linesize[2] *= -1;  
  
  
  
  
  
    sws_scale(scxt,m_pRGBFrame->data,m_pRGBFrame->linesize,0,c->height,m_pYUVFrame->data,m_pYUVFrame->linesize);  
  
  
  
    int got_packet_ptr = 0;  
  
    av_init_packet(&avpkt);  
  
    avpkt.data = outbuf;  
  
    avpkt.size = outbuf_size;  
  
    u_size = avcodec_encode_video2(c, &avpkt, m_pYUVFrame, &got_packet_ptr);  
  
    if (u_size == 0)  
  
    {  
  
     fwrite(avpkt.data, 1, avpkt.size, f);  
  
    }  
  
  } 
  
  
  
  fclose(f);   
  
  delete []m_pRGBFrame;  
  
  delete []m_pYUVFrame;  
  
  delete []rgb_buff;  
  
  free(outbuf);  
  
  avcodec_close(c);  
  
  av_free(c);  
  
  }

  I want to use this code to record screen by encoding screenshots. what fps,gop size or other parameters i can use to reduce size of video.