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• Video streaming- control frame rate x264

  3 mars 2017, par H.A

  I’m new to video coding, I found this https://github.com/RafaelPalomar/H264LiveStreamer application code very useful to my project. I want to live stream a webcam over RTP . However, I’m having problem selecting the Frame Per Seconds (FPS). below is the function that controls the encoding param.

  void x264Encoder::initilize()
  
  {
  
    x264_param_default_preset(&parameters, "veryfast", "zerolatency");
  
    parameters.i_log_level =  X264_LOG_DEBUG;
  
    parameters.i_threads = 1;
  
    parameters.i_width = 640;
  
    parameters.i_height = 480;
  
    parameters.i_fps_num = 25;
  
    parameters.i_fps_den = 1;
  
    parameters.i_keyint_max = 25;
  
    parameters.b_intra_refresh = 1;
  
    parameters.rc.i_rc_method = X264_RC_CRF;
  
    parameters.rc.i_vbv_buffer_size = 1000000;
  
    parameters.rc.i_vbv_max_bitrate = 90000;
  
    parameters.rc.f_rf_constant = 25;
  
    parameters.rc.f_rf_constant_max = 35;
  
    parameters.i_sps_id = 7;
  
    // the following two value you should keep 1
  
    parameters.b_repeat_headers = 1;    // to get header before every I-Frame
  
    parameters.b_annexb = 1; // put start code in front of nal. we will remove start code later
  
    x264_param_apply_profile(&parameters, "baseline");
  
  
  
    encoder = x264_encoder_open(&parameters);
  
    x264_picture_alloc(&picture_in, X264_CSP_I420, parameters.i_width, parameters.i_height);
  
    picture_in.i_type = X264_TYPE_AUTO;
  
    picture_in.img.i_csp = X264_CSP_I420;
  
    // i have initilized my color space converter for BGR24 to YUV420 because my opencv video capture gives BGR24 image. You can initilize according to your input pixelFormat
  
    convertContext = sws_getContext(parameters.i_width,parameters.i_height, PIX_FMT_BGR24, parameters.i_width,parameters.i_height,PIX_FMT_YUV420P, SWS_FAST_BILINEAR, NULL, NULL, NULL);
  
  }

  I’m using VLC as client whatever number i set i_fps_num to, I always get 12-14 FPS. fore example, in VLC Codec tab shows 25 FPS but in Stream statistics tab it shows it only display 13 FPS on average. here is the X264 encoder output

  x264 [debug]: frame=  72 QP=22.24 NAL=2 Slice:P Poc:144 I:97   P:116  SKIP:987  size=1464 bytes
  
  x264 [info]: frame I:1     Avg QP:20.06  size: 17848
  
  x264 [info]: frame P:72    Avg QP:22.12  size:  1337
  
  x264 [info]: mb I  I16..4: 40.2%  0.0% 59.8%
  
  x264 [info]: mb P  I16..4:  3.1%  0.0%  2.3%  P16..4:  8.3%  2.0%  0.6%  0.0%  0.0%    skip:83.7%
  
  x264 [info]: coded y,uvDC,uvAC intra: 53.6% 46.4% 7.4% inter: 3.0% 1.6% 0.0%
  
  x264 [info]: i16 v,h,dc,p: 11% 65% 12% 12%
  
  x264 [info]: i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 15% 46% 16%  3%  4%  3%  5%  3%  6%
  
  x264 [info]: i8c dc,h,v,p: 46% 42% 10%  2%
  
  x264 [info]: kb/s:312.60

  the last frame number that was encoded is 72 while in VLC stream statistics it shows that 133 frames are Displayed and 66 blocks are decoded for 10 seconds streaming in addition the video playback is bursty.

  my question is how to change the x264 parameters to get 25 FPS ?

• Compressing videos from a smartphone

  9 novembre 2016, par fejesjoco

  I have a Nexus 6p with the stock camera. It’s set to record at 1080p, 30fps. Here’s a 5 second sample (11 MB).

  Videos from this phone come out at about 17 Mbps on average. I tried to compress it with ffmpeg with -c:v libx264 -crf 23 -preset veryslow, the result comes out at about 5.5 MB, which is about 9 Mbps.

  I think this bitrate is a bit too much. When I look at torrent file listings, I can see high quality videos at 3 GB in size on average, and if such a movie is 90 minutes long on average, that is about 4-5 Mbps which sounds okay.

  I’m wondering, why the big difference ? I can notice that my video is noisy/grainy (which is expected from a phone), and that might reduce compressibility. I tried a few ffmpeg filters, like hqdn3d and atadenoise, but the noise mostly remained (maybe I didn’t play with it enough). Then I figured, the video is also shaky (which is also expected), and that might reduce compressibility too (and even makes temporal noise filtering less effective). I tried to stabilize it with the deshake filter, but that didn’t help either.

  I know I could just limit the bandwidth to whatever I like, but there must be a reason why ffmpeg thinks it needs a high bandwidth to maintain a certain quality, and a lower bandwidth would just decrease the quality.

  Why do these videos have such a high bitrate ? What’s the best way to compress them more while keeping or even increasing their quality ?

• 2D video to VR 360° "wall of TV's" ?

  1er septembre 2020, par ƬƦƖƝƛ

  What would be involved in creating a 360° "wall of TV's" style VR video from a bunch of 2d videos ? (surrounding the viewer)

  


  Is that complexity of rendering even possible using typical software (ffmpeg ?) on an average home computer ?

  


  
  
[okay, maybe not THAT complex !]