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• How do I save `RTSP` streams as `*.mp4` files in Golang ? [closed]

  14 septembre 2021, par Clancy Zeng

  I need to use Golang to save the data from the RTSP stream to a *.mp4 video file for a specified length of time.

  


  I wanted to install an FFmpeg application and then call a command like this from Golang to solve my needs.

  


  


  ffmpeg -i rtsp ://192.168.108.132:8554/profile0 -r 16 -tt 60 /tmp/test.mp4

  


  


  But installing FFMPEG takes up hundreds of megabytes of space.So this idea was rejected by the leadership.

  


  Is there a pure Golang implementation library that can address my needs ?Or is there a golang-only library that parses RTSP streams and saves them as *.MP4 video files ?

  


• Trying to save frames as colored image using Ffmpeg in C++

  2 septembre 2021, par Tolga

  I am new to FFmpeg and I am trying to save the video frames as colored images. I have achieved saving them as grayscale using Netpbm, however, I need to save the frames as colored. I have tried implementing the code in this link.

  


  However, I get an error :

  


  'Exception thrown at 0x00E1FC4F (swscale-5.dll) in VideoDecoding2.exe:
 0xC0000005: Access violation writing location 0xCCCCCCCC.'


  


  Is there any way to improve this code or another way to save frames as colored ?

  


  Here is my code below.

  


  

  • src_pix_fmt is AV_PIX_FMT_YUV420p.

  


  • dst_pix_fmt is AV_PIX_FMT_RGB24.

  


  


  src_pix_fmt = avcc->pix_fmt;

src_width = avcc->width;
src_height = avcc->height;

dst_width = src_width;
dst_height = src_height;

numBytes = av_image_get_buffer_size(dst_pix_fmt, dst_width, dst_height, 0);

buffer = (uint8_t*)av_malloc(numBytes);

if ((ret = av_image_alloc(src_data, src_linesize, src_width, src_height, src_pix_fmt, 16)) < 0)
{
    printf("Couldn't allocate source image.\n");
    return 0;
}

av_image_fill_arrays(frameRGB->data, frameRGB->linesize, buffer, dst_pix_fmt, dst_width, dst_height, 0);

while (av_read_frame(avfc, packet) >= 0)
{
    ret = avcodec_send_packet(avcc, packet);
    if (ret < 0)
    {
        printf("Packets could not supplied to decoder.\n");
        return -1;
    }

    ret = avcodec_receive_frame(avcc, frame);
    printf("%d", ret);

    if (packet->stream_index == videoStream)
    {
        sws_ctx = sws_getContext(src_width, src_height, src_pix_fmt,
            dst_width, dst_height, dst_pix_fmt,
            SWS_BILINEAR, NULL, NULL, NULL);

        if (!sws_ctx)
        {
            printf("Cannot create scale context for conversion\n"
                "fmt:%s s:%dx%d --> fmt:%s s:%dx%d\n",
                av_get_pix_fmt_name(src_pix_fmt), src_width, src_height,
                av_get_pix_fmt_name(dst_pix_fmt), dst_width, dst_height);
            return 0;
        }

        sws_scale(sws_ctx, (const uint8_t* const*)frame->data, frame->linesize, 0, frame->height, dst_data, dst_linesize);

        FILE* f;
        char szFilename[32];
        int y;

        snprintf(szFilename, sizeof(szFilename), "frame%d.ppm", avcc->frame_number);
        fopen_s(&f, szFilename, "wb");
        
        if (f == NULL)
        {
            printf("Couldn't open file.\n");
            return 0;
        }
        
        fprintf(f, "P6\n%d %d\n255\n", dst_width, dst_height);

        for (y = 0; y < dst_height; y++)
            fwrite(frameRGB->data[0] + y * frameRGB->linesize[0], 1, dst_width * 3, f);
        
        fclose(f);
    }
}


  


• FFmpeg av_read_frame returns packets from audio stream

  1er août 2018, par yultan

  I am currently trying to learn the FFmpeg API, following this tutorial. However, I already have issues with the first lesson on video decoding. My code is basically the same as the one from the tutorial except I am using C++. My issue is that the video stream does not match the one from the packet returned by av_read_frame.

  The video stream is obtained looping on the available streams until the video stream is found.

  for(int i = 0; i < pFormatCtx->nb_streams; i++) { // nb_streams == 2
  
  
  
      if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO) {
  
          videoStream = i; 
  
          break; // videoStream == 0
  
      }
  
  }

  Then when retrieving the frame data, it seams grabbing the audio channel.

  while(av_read_frame(pFormatCtx, &packet) >= 0) { // read returns 0
  
  
  
      // Is this a packet from the video stream?
  
      if(packet.stream_index == videoStream) { 
  
          //packet.stream_index == 1, which correspond to the audio stream
  
      } 
  
  }

  I have not found examples online where this test is actually failing. Have I miss some way to specify the stream_index that is not in the tutorial ? Maybe the tutorial is not up to date and is doing something wrong ? If so, what is the correct way to extract the frame data ? In case that matters, I am using the latest FFmpeg 4.0.2 build, on Windows 64-bits, compiling with Visual Studio 2017.

  On videos with no sound, the two streams match and I am able to decode and display the frames correctly.