Recherche avancée

Sur d’autres sites (7647)

• 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

• 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..!

• lavc/vaapi_encode_h265 : Add GPB frame support for hevc_vaapi

  17 mars 2022, par Linjie Fu

  lavc/vaapi_encode_h265 : Add GPB frame support for hevc_vaapi
  Use GPB frames to replace regular P/B frames if backend driver does not
  
  support it.
   GPB :
  
      Generalized P and B picture. Regular P/B frames replaced by B
  
      frames with previous-predict only, L0 == L1. Normal B frames
  
      still have 2 different ref_lists and allow bi-prediction
  Signed-off-by : Linjie Fu <linjie.fu@intel.com>
  
  Signed-off-by : Fei Wang <fei.w.wang@intel.com>
  

  • [DH] libavcodec/vaapi_encode.c
  • [DH] libavcodec/vaapi_encode.h
  • [DH] libavcodec/vaapi_encode_h265.c