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• How to force usage of specific codec with ffmpeg ?

  4 septembre 2013, par Srv19

  I am trying to read a certain video file using ffmpeg, and have run into a bit of trouble.

  This is the code that starts to read it :

  int _tmain(int argc, _TCHAR* argv[])
  
  {
  
      if (argc < 2)
  
      {
  
          fprintf( stderr, "Filename is needed as an argument\n" );  
  
          return 1;  
  
      }
  
      /* register all formats and codecs */
  
      av_register_all();
  
      AVFormatContext* fmt_ctx = NULL;
  
      /* open input file, and allocate format context */
  
      const char *src_filename = argv[1];
  
      if (avformat_open_input(&fmt_ctx, src_filename, NULL, NULL) < 0) {
  
          fprintf(stderr, "Could not open source file %s\n", src_filename);
  
          abort();
  
      }
  
      /* retrieve stream information */
  
      AVDictionary *      options;
  
      int res = avformat_find_stream_info(fmt_ctx, &options);
  
      if (res < 0) {
  
          fprintf(stderr, "Could not find stream information\n");
  
          abort();
  
      }
  
      ...
  
  }

  I am consistently getting the following message :

  [avi @ 005f2fe0] Could not find codec parameters for stream 0 (Video :
  none (GREY / 0x59455247), 1280x1024) : unknown codec

  Consider increasing the value for the 'analyzeduration' and 'probesize' options

  I get the same message when i run ffmpeg tool on the same file.

  However, i know what is in the video stream - raw video data with YUV8 format. In fact, when i pass that to ffmpeg via -c:v rawvideo option, there is no problem. Recoding, transforming etc - ffmpeg does it like the magic tool it is.

  Now, the question is : when using ffmpeg api, what is the equivalent of that option ? I desperately need access to the frames of file.

• Merge commit 'd7320ca3ed10f0d35b3740fa03341161e74275ea'

  31 octobre 2017, par James Almer

  Merge commit 'd7320ca3ed10f0d35b3740fa03341161e74275ea'
  * commit 'd7320ca3ed10f0d35b3740fa03341161e74275ea' :
  
    arm : Avoid using .dn register aliases
  Merged-by : James Almer <jamrial@gmail.com>
  

  • [DH] configure
  • [DH] libavcodec/arm/vc1dsp_init_neon.c
  • [DH] libavcodec/arm/vc1dsp_neon.S

• C++ ffmpeg sws_getCachedContext seg fault when reading opengl buffer

  3 juillet 2022, par user19068953

  I made a program that draws some stuff on opengl, then reads the frames on the screen as rgba and encodes it as a yuv420 video, but I get a segfault when I try to send the red opengl frame to sws_getCachedContext. I used the muxing.c as the encoder and my code is as follows (I used align 256 because i have another framebuffer that uses 128) :

  


      constexpr int ALIGNMENT = 256;
    if (posix_memalign((void**)&state.glBuffer, ALIGNMENT, gl_width * gl_height * 4) != 0) 
    {
        VI_ERROR("Couldn't allocate frame buffer ");
        return false;
    }
    REGISTER("done, returning");
    return true;


  


  Then i read the frame after drawing the stuff i want :

  


          glReadPixels(0, 0,
                 gl_width, gl_height, 
                 GL_RGBA, GL_UNSIGNED_BYTE, 
                 (GLvoid*) state.glBuffer);


  


  The window is the same size as the gl_buffer (I know the result will be flipped, thats ok)

  


  And finally i send it to the encoder(rgb_data is glBuffer) :

  


  void video_encoder::set_frame_yuv_from_rgb(AVFrame *frame, struct SwsContext *sws_context) {
    const int in_linesize[1] = { 4 * width };

width = gl_width;
height = gl_height;
sws_context = sws_getCachedContext(sws_context,
        width, height, AV_PIX_FMT_RGBA,
        width, height, AV_PIX_FMT_YUV420P,
        0, 0, 0, 0);
        
sws_scale(sws_context, (const uint8_t * const *)&rgb_data, in_linesize, 0,
        height, frame->data, frame->linesize);
}


  


  I get a seg fault on sws_getCachedContext any idea why this happens and how do i fix it ?

  


  Edit : width = 512, height = 256, valgrind says : Invalid read of size 16.