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• Bad pictures displayed by SDL after decoded using ffmpeg from a rtp stream

  2 juin 2015, par clouyfsail

  My program is a H323 endpoint.I receive a H263 rtp stream from H323 protocol stack,and I need to decode and play it with SDL2.0.

  Here is what I did.Firstly I assembled rtp packets into H263 frames myself before decode them.After I got a H263 frame, I sent it to ffmpeg to decode it.Just like this :

  void DecodeFrame(uint8_t *buff, unsigned size)
  
  {
  
      //There is no rtp header in this buff,just rtp payload,and this is a 
  
      //a complete frame
  
      if(!buff || size <= 0)
  
          return;
  
      AVPacket packet;
  
      av_init_packet(&packet);
  
      int got_picture = 0;
  
  
  
      packet.data = buff;
  
      packet.size = size;
  
  
  
      //I have assigned a H263 codec and initialized corresponding structures.
  
      int len = avcodec_decode_video2(m_codec_context, m_picture, 
  
                                      &got_picture, &packet);
  
  
  
      if(len < 0)
  
          return;
  
  
  
      if (got_picture)
  
      {
  
          packet.pts = AV_NOPTS_VALUE;
  
          sws_scale(m_sws_context, (const uint8_t *  const *)m_picture->data,
  
                    m_picture->linesize, 0, m_codec_context->height, m_yuv_frame->data,
  
                    m_yuv_frame->linesize);
  
  
  
          SDL_UpdateYUVTexture(m_sdl_texture, &m_sdl_rect, 
  
                               m_yuv_frame->data[0], m_yuv_frame->linesize[0],
  
                               m_yuv_frame->data[1], m_yuv_frame->linesize[1],
  
                               m_yuv_frame->data[2], m_yuv_frame->linesize[2]);
  
          SDL_RenderClear(m_sdl_renderer);
  
          SDL_RenderCopy(m_sdl_renderer, m_sdl_texture, nullptr, &m_sdl_rect);
  
          SDL_RenderPresent(m_sdl_renderer);
  
      }
  
  }

  It worked, but not as I wished.At the begining of the play,I got a foggy picture,then it turned to clear in a strange way.The image became clear row by row.After that,it turned to foggy sharply if the scene changed drastically(In remote endpoint,the source of video is a camera),and it became clear slowly row by row again.This confuses me much.I want to know why this happened.

• Does simple rescaling from 1080p to frame height of 720 lead to 720p ?

  12 août 2015, par nburk

  I want to convert a 1080p to 720p and also lower resolutions eventually.

  I have been using ffmpeg for all my video processing activities so far, and would simply approach this task using the following command :

  ffmpeg -i tos.mov -vf scale=-1:720 tos_0x720.mov

  I understand that this will rescale my video to a new frame size having 720 pixels set as a fixed height and the width dynamically calculated.

  What I am not sure about are the implications regarding the quality factors of the video when using ffmpeg this way.

  1. Is it valid to assume that running this command will output a perfect HD 720p quality video ?
  2. What would be a benefit of using dedicated video conversion software to accomplish my goal compared to running the above command ?

• avformat/movenc : add muxing support for Dolby TrueHD streams

  1er août 2019, par James Almer

  avformat/movenc : add muxing support for Dolby TrueHD streams
  Signed-off-by : James Almer <jamrial@gmail.com>
  

  • [DH] libavformat/movenc.c
  • [DH] libavformat/version.h