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• How to convert audio stream from PureTool/CVS video ?

  1er janvier 2013, par Mark

  I apologize if there is a better place to post this. I recently came across a couple CVS single-use video cameras that I had been using back in 2005. I still have the USB cable I made and now that I've switched to Mac I can use Puretool to extract the old videos from the cameras. The problem I'm having is that I can only hear the audio when viewing the videos with VLC media player. I read on PureTools site, a common problem is that the audio codec used is incompatible with Quicktime and the audio stream needs to be converted. There is a link on their site to a program called FixSound which is purported to fix this, but the link is dead and I've been unable to find any further information about this. If anyone could point me in the right direction, I'd be very grateful. All the videos I'm dealing with are from the first year of my son's life and I'd really like to be able to archive them in a more uniform format. I would think this would be possible to do using Adobe Audition or some other program in Adobe's CS6 Master Collection but I've only dealt with Photoshop, Illustrator, Dreamweaver, Flash & Fireworks. I have no experience with audio or video yet.

  Thanks,

  Mark

• Decode a video file from memory using libav

  21 octobre 2015, par Dídac Pérez

  Supose I have an entire video file in memory and I want to use libav to decode the whole frames. How should I do it ? The point is that I can do it reading directly from a file using avformat_open_input() function but I do need to do it from a file which is stored in memory.

  My AVIOContext implementation :

  class AVIOMemContext
  
  {
  
  
  
  public:
  
  
  
      AVIOMemContext(char* videoData, const int videoLen)
  
      {
  
          // Output buffer
  
          bufferSize = 32768;
  
          buffer = static_cast(av_malloc(bufferSize));
  
  
  
          // Internal buffer
  
          pos = 0;
  
          this->videoData = videoData;
  
          this->videoLen = videoLen;
  
  
  
          ctx_ = avio_alloc_context((unsigned char*) buffer, bufferSize, AVIO_FLAG_READ, this, &AVIOMemContext::read, &AVIOMemContext::write, &AVIOMemContext::seek);
  
      }
  
  
  
      ~AVIOMemContext()
  
      {
  
          av_free(videoData);
  
      }
  
  
  
      static int read(void *opaque, unsigned char *buf, int buf_size)
  
      {
  
          AVIOMemContext* This = static_cast(opaque);
  
  
  
          // Read from pos to pos + buf_size
  
          if (This->pos + buf_size > This->videoLen)
  
          {
  
              int len = This->videoLen - This->pos;
  
              memcpy(buf, This->videoData + This->pos, len);
  
              return len;
  
          }
  
          else
  
          {
  
              memcpy(buf, This->videoData + This->pos, buf_size);
  
              return buf_size;
  
          }
  
      }
  
  
  
      static int write(void *opaque, unsigned char *buf, int buf_size)
  
      {
  
          /*
  
          AVIOMemContext* This = static_cast(opaque);
  
          return fwrite(buf, 1, buf_size, This->f_);
  
          */
  
  
  
          return 0;
  
      }
  
  
  
      static int64_t seek(void *opaque, int64_t offset, int whence)
  
      {
  
          AVIOMemContext* This = static_cast(opaque);
  
  
  
          if (offset + whence > This->videoLen)
  
          {
  
              This->pos = This->videoLen;
  
  
  
              return -1;
  
          }
  
          else
  
          {
  
              This->pos = offset + whence;
  
  
  
              return 0;
  
          }
  
      }
  
  
  
      AVIOContext *get_avio()
  
      {
  
          return ctx_;
  
      }
  
  
  
  private:
  
  
  
      // Output buffer
  
      int bufferSize;
  
      char* buffer;
  
  
  
      // Internal buffer
  
      int pos;
  
      char* videoData;
  
      int videoLen;
  
  
  
      AVIOContext* ctx_;
  
  
  
  };

  My current code :

  [...]
  
  
  
  av_register_all();
  
  avcodec_register_all();
  
  
  
  AVFormatContext* context;
  
  AVCodec* pCodec;
  
  AVPacket packet;
  
  AVCodecContext* pCodecCtx;
  
  int video_stream_index;
  
  int res;
  
  int got_picture;
  
  
  
  // Init variables and objects
  
  context = avformat_alloc_context();
  
  
  
  AVIOMemContext priv_ctx(videoData, videoLen); 
  
  context->pb = priv_ctx.get_avio();
  
  
  
  res = avformat_find_stream_info(context, NULL);
  
  
  
  if (res < 0)
  
  {
  
      // Error
  
      avformat_free_context(context);
  
  
  
      return 0;
  
  }
  
  
  
  // Obtain the video stream of the total set of streams
  
  for (unsigned int k = 0; k < context->nb_streams; ++k)
  
  {
  
      if (context->streams[k]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
  
          video_stream_index = k;
  
      context->streams[k]->codec->time_base.den = 90000;
  
  }
  
  
  
  pCodecCtx = context->streams[video_stream_index]->codec;
  
  pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
  
  
  
  avcodec_open(pCodecCtx, pCodec);
  
  
  
  //allocate video frame
  
  AVFrame *pFrame = avcodec_alloc_frame();
  
  
  
  unsigned int nFrame = 0;
  
  
  
  while (av_read_frame(context, &packet) >= 0)
  
  
  
  [...]

  Thanks in advance,

  Dídac Pérez

• lavf : introduce AVFMT_TS_NEGATIVE

  3 avril 2013, par Luca Barbato

  lavf : introduce AVFMT_TS_NEGATIVE
  Most formats do not support negative timestamps, shift them to avoid
  
  unexpected behaviour and a number of bad crashes.
  CC:libav-stable@libav.org
  Signed-off-by : Anton Khirnov <anton@khirnov.net>
  
  Signed-off-by : Luca Barbato <lu_zero@gentoo.org>
  

  • [DBH] libavformat/avformat.h
  • [DBH] libavformat/ffmenc.c
  • [DBH] libavformat/framecrcenc.c
  • [DBH] libavformat/md5enc.c
  • [DBH] libavformat/mux.c
  • [DBH] libavformat/oggenc.c
  • [DBH] tests/ref/lavf/asf
  • [DBH] tests/ref/lavf/mkv
  • [DBH] tests/ref/lavf/mpg
  • [DBH] tests/ref/lavf/ts
  • [DBH] tests/ref/seek/lavf-asf
  • [DBH] tests/ref/seek/lavf-mkv
  • [DBH] tests/ref/seek/lavf-mpg
  • [DBH] tests/ref/seek/lavf-ts