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• Confused about x264 and encoding video frames

  26 février 2015, par spartygw

  I built a test driver for encoding a series of images I have captured. I am using libx264 and based my driver off of this guy’s answer :

  StackOverflow link

  In my case I am starting out by reading in a JPG image and converting to YUV and passing that same frame over and over in a loop to the x264 encoder.

  My expectation was that since the frame is the same that the output from the encoder would be very small and constant.

  Instead I find that the NAL payload is varied from a few bytes to a few KB and also varies highly depending on the frame rate I specify in the encoder parameters.

  Obviously I don’t understand video encoding. Why does the output size vary so much ?

  int main() 
  
  {
  
    Image image(WIDTH, HEIGHT);
  
    image.FromJpeg("frame-1.jpg");
  
  
  
    unsigned char *data = image.GetRGB();
  
  
  
    x264_param_t param;
  
  
  
    x264_param_default_preset(&param, "fast", "zerolatency");
  
    param.i_threads = 1;
  
    param.i_width = WIDTH;
  
    param.i_height = HEIGHT;
  
    param.i_fps_num = FPS;
  
    param.i_fps_den = 1;
  
  
  
    // Intra refres:
  
    param.i_keyint_max = FPS;
  
    param.b_intra_refresh = 1;
  
  
  
    //Rate control:
  
    param.rc.i_rc_method = X264_RC_CRF;
  
    param.rc.f_rf_constant = FPS-5;
  
    param.rc.f_rf_constant_max = FPS+5;
  
  
  
    //For streaming:
  
    param.b_repeat_headers = 1;
  
    param.b_annexb = 1;
  
  
  
    x264_param_apply_profile(&param, "baseline");
  
  
  
    // initialize the encoder
  
    x264_t* encoder = x264_encoder_open(&param);
  
    x264_picture_t pic_in, pic_out;
  
    x264_picture_alloc(&pic_in, X264_CSP_I420, WIDTH, HEIGHT);
  
    // X264 expects YUV420P data use libswscale 
  
    // (from ffmpeg) to convert images to the right format
  
    struct SwsContext* convertCtx =
  
          sws_getContext(WIDTH, HEIGHT, PIX_FMT_RGB24, WIDTH, HEIGHT,
  
                         PIX_FMT_YUV420P, SWS_FAST_BILINEAR,
  
                         NULL, NULL, NULL);
  
  
  
    // encoding is as simple as this then, for each frame do:
  
    // data is a pointer to your RGB structure
  
    int srcstride = WIDTH*3; //RGB stride is just 3*width
  
    sws_scale(convertCtx, &data, &srcstride, 0, HEIGHT,
  
              pic_in.img.plane, pic_in.img.i_stride);
  
    x264_nal_t* nals;
  
    int i_nals;
  
    int frame_size =
  
          x264_encoder_encode(encoder, &nals, &i_nals, &pic_in, &pic_out);
  
  
  
    int max_loop=15;
  
    int this_loop=1;
  
  
  
    while (frame_size >= 0 && --max_loop)
  
    {
  
        cout << "------------" << this_loop++ << "-----------------\n";
  
        cout << "Frame size = " << frame_size << endl;
  
        cout << "output has " << pic_out.img.i_csp << " colorspace\n";
  
        cout << "output has " << pic_out.img.i_plane << " # img planes\n";
  
  
  
        cout << "i_nals = " << i_nals << endl;
  
        for (int n=0; n

• ffmpeg QSV hardware encoder with x11grab screen capture

  11 janvier 2020, par Toby Eggitt

  I believe I have built ffmpeg with support for my motherboard’s Intel graphics processor chip, but I have not succeeded in showing this working in any way. My goal is to use it for screen capture (the ffmpeg I built does capture screen successfully using the software encoding, but this is far too slow to be useful—it manages about 12fps at a very modest quality).

  My main problem—I think—is that I don’t know how to use these encoders, the examples I found all fail, which makes me suspect that what I’ve built is broken in some way. However, I also have no idea how I can verify that I built this correctly, but the following are true :

  • The five components that I built to get to this all compiled without
    errors (they were libva, gmmlib, intel-media-driver, libmfx, and
    ffmpeg
  • The output of ffmpeg -encoders includes four encoders with _qsv in
    their names including h264_qsv
  • Most of the commands I have tried result in output of this form :

      [h264_qsv @ 0x55ef1dc72040] Low power mode is unsupported
  
      [h264_qsv @ 0x55ef1dc72040] Current frame rate is unsupported
  
      [h264_qsv @ 0x55ef1dc72040] Current picture structure is unsupported
  
      [h264_qsv @ 0x55ef1dc72040] Current resolution is unsupported
  
      [h264_qsv @ 0x55ef1dc72040] Current pixel format is unsupported
  
      [h264_qsv @ 0x55ef1dc72040] some encoding parameters are not supported by the QSV runtime. Please double check the input parameters.
  
      Error initializing output stream 0:0 -- Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height

  I have the impression this thing might be fussy about many parameters of this sort but have no idea where to find out what it would like. Any suggestions at all, how to verify it, or better yet, how to issue a command that captures screen and encodes with the hardware, would be most welcome.

• recording live stream video from tv card using ffmpeg at window [on hold]

  6 décembre 2013, par user2688423

  I want to record live stream every 1 second from tv card(tv signal) using ffmpeg in window.

  first of all, to record live video from tv card, I tried below.

  1. First I tried this.

  ffmpeg -list_devices true -f dshow -i dummy

  then the result is

  " [dshow @ 000000000024e6fe0] DirectShow video devices
  [dshow @000000000024e6fe0] "SKYTV HD USB Maxx Video Capture"
  [dshow @
  000000000024e6fe0] DirectShow audio devices
  [dshow @
  000000000024e6fe0] "Analog Audio In(SKYTV HD USB Ma" "

  so I tried

  ffmpeg -f dshow -i video="SKYTV HD USB Maxx Video Capture" -r 20
  -threads 0 D ://test.mkv

  But it didn't work. the Error message is

  "[dshow@000000000034d920] Could not run filter
  video=SKYTV HD USB
  Maxx Video Capture : Input/output error"

  I use the device called 'SKYTV HD USB Maxx Video Capture' for getting tv signal(TV card).

  1. The First way deosn't work, I tried different way.

  ffmpeg -y -f vfwcap -i list

  then the result is
  "

  [dshow @ 00000000003fd760] Driver 0

  [dshow @ 00000000003fd760] Microsoft WDM Image Capture (Win32)
  [dshow @ 00000000003fd760] Version : 6.1.7601.17514 list : Input/output error

  "

  so I tried

  ffmpeg -y -f vfwcap -r 25 -i 0 D ://out.mp4

  then, there is some out.mp4 file in D drive but the file is nothing.
  (I think it is not TV signal)

  what should i do to record live video every 1 second from tv card(tv signal) using ffmpeg in window ? And How can I set channel at tvcard(Because I want to get tv signal, there are many channels).

  Please help..!