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• FFMPEG : how to save input camera stream into the file with the SAME codec format ?

  19 janvier 2014, par user3211926

  I have the camera-like device that produces video stream and passes it into my Windows-based machine via USB port.

  Using the command :

  ffmpeg -y -f vfwcap -i list

  I see that (as expected) FFmpeg finds the input stream as stream #0.

  Using the command :

  ffmpeg -y -f vfwcap -r 25 -i 0 c:\out.mp4

  I can successfully save the input stream into the file.

  From the log I see :

  Stream #0:0 : Video : rawvideo (UYVY / 0x59565955), uyvy422, 240x320, 25 tbr, 1k tbn, 25 tbc
  No pixel format specified, yuv422p for H.264 encoding chosen.

  So, my input format is transcoded to yuv422p.

  My question :

  • How can I cause FFmpeg to save my input video stream into out.mp4 WITHOUT transcoding - actually, to copy input stream to output file as close as possible, with the same format ?

• checkasm : x86 : properly save rdx/edx in checked_call()

  16 août 2015, par Henrik Gramner

  checkasm : x86 : properly save rdx/edx in checked_call()
  If the return value doesn’t fit in a single register rdx/edx can in some
  
  cases be used in addition to rax/eax.
  Doesn’t affect any of the existing checkasm tests but might be useful later.
  Also comment the relevant code a bit better.
  

  • [DH] tests/checkasm/x86/checkasm.asm

• FFMPEG - How to save audio stream detached from video to file whithout transcoding

  15 septembre 2015, par Tony Than

  I try to use fwrite() to save audio stream. But, generated file can not be opened.
  At the same time, I also try to use av_frame_write() to write packet. But, it can not write.
  Please help me with this problem. How to write audio stream without transcoding....

  /* open the input file with generic avformat function */
  
  err = avformat_open_input(input_format_context, filename, NULL, NULL);
  
  if (err < 0) {
  
      return err;
  
  }
  
  
  
  /* If not enough info to get the stream parameters, we decode the
  
     first frames to get it. (used in mpeg case for example) */
  
  ret = avformat_find_stream_info(*input_format_context, 0);
  
  if (ret < 0) {
  
      av_log(NULL, AV_LOG_FATAL, "%s: could not find codec parameters\n", filename);
  
      return ret;
  
  }
  
  
  
  /* dump the file content */
  
  av_dump_format(*input_format_context, 0, filename, 0);
  
  
  
  for (size_t i = 0; i < (*input_format_context)->nb_streams; i++) {
  
      AVStream *st = (*input_format_context)->streams[i];
  
      if (st->codec->codec_type == AVMEDIA_TYPE_AUDIO) {
  
          FILE *file = NULL;
  
          file = fopen("C:\\Users\\MyPC\\Downloads\\test.aac", "wb");
  
          AVPacket reading_packet;
  
          av_init_packet(&reading_packet);
  
          while (av_read_frame(*input_format_context, &reading_packet) == 0) {
  
              if (reading_packet.stream_index == (int) i) {
  
              fwrite(reading_packet.data, 1, reading_packet.size, file);
  
              }
  
              av_free_packet(&reading_packet);   
  
          }
  
          fclose(file);
  
  
  
          return 0;
  
      }
  
  }