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• ffmpeg to change video from 30 to 60fps to double speed without re-encoding

  29 novembre 2018, par user3144514

  First, I have looked at the older questions asking the same, but the responses do not work.
  Adding -r 30 or 60 to the input file does not impact the output, nor does setting it for the output, which remains unchanged.

  I am handling a very large number of files from 1 to 22 gigs recorded (with audio) in 30fps that need to be re-posted as 60pfs, with the corresponding speed increase.

  I toyed with ffmpeg a bit and came up with this..

  -filter_complex "[0:v]setpts=0.50*PTS[v];[0:a]atempo=2.0[a]" -map "[v]" -map "[a]" -vcodec:v libx264

  It works fine, but to have to wait out a complete re-encoding of the video and audio to produce the same video with the fps changed seems like an insane waste of time.

  Am I missing something simple ? Is there not a way to -c copy with a new fps playback rate on the resulting file ?
  (if it still has to recode the audio to maintain sync that’s fine, audio is quick enough it doesn’t much matter)

• FFmpeg Not Transcoding In Real Time

  2 décembre 2018, par Nimble

  Been setting up a recording build for a friend to resemble mine, but I can’t seem to get things to work in real-time despite sufficient (as far as I can tell) hardware.

  System specs : 8600K, GTX 1050ti, 16Gb RAM, 1tb 860 EVO

  Test command :

  ffmpeg -y -hide_banner -thread_queue_size 9999 -indexmem 9999 -guess_layout_max 0 -f dshow -rtbufsize 2147.48M `
  
  -video_size 1920x1080 -framerate 60 `
  
  -i video="@device_pnp_\\?\usb#vid_07ca&pid_0570&mi_00#7&3886ab1a&0&0000#{65e8773d-8f56-11d0-a3b9-00a0c9223196}\global":audio="@device_cm_{33D9A762-90C8-11D0-BD43-00A0C911CE86}\wave_{0A494693-5F33-4304-88D7-394757E09648}" `
  
  -thread_queue_size 9999 -indexmem 9999 -guess_layout_max 0 -f dshow -rtbufsize 2147.48M `
  
  -video_size 1920x1080 -framerate 60 `
  
  -i video="@device_pnp_\\?\usb#vid_07ca&pid_0570&mi_00#7&24df76f&0&0000#{65e8773d-8f56-11d0-a3b9-00a0c9223196}\global":audio="@device_cm_{33D9A762-90C8-11D0-BD43-00A0C911CE86}\wave_{0E6F0DEF-2B29-4117-8D30-13F01160AC5B}" `
  
  -map 0:0,0:1 -map 0:1 -c:v h264_nvenc -r 60 -rc-lookahead 120 -forced-idr 1 -strict_gop 1 -sc_threshold 0 -flags +cgop `
  
  -force_key_frames "expr:gte(t,n_forced*2)" -preset: llhp -pix_fmt nv12 -b:v 250M -minrate 250M -maxrate 250M `
  
  -bufsize 250M -c:a aac -ar 44100 -b:a 384k -ac 2 -af "aresample=async=250" -vsync 1 -ss 00:00:00.000 `
  
  -max_muxing_queue_size 9999 -f segment -segment_time 600 -segment_wrap 9 -reset_timestamps 1 `
  
  -segment_format_options max_delay=0 C:\Users\Jordan\Videos\FFmpeg\Left\Left%02d.ts `
  
  -map 1:0,1:1 -map 1:1 -c:v h264_nvenc -r 60 -rc-lookahead 120 -forced-idr 1 -strict_gop 1 -sc_threshold 0 -flags +cgop `
  
  -force_key_frames "expr:gte(t,n_forced*2)" -preset: llhp -pix_fmt nv12 -b:v 250M -minrate 250M -maxrate 250M `
  
  -bufsize 250M -c:a aac -ar 44100 -b:a 384k -ac 2 -af "aresample=async=250" -vsync 1 -ss 00:00:00.000 `
  
  -max_muxing_queue_size 9999 -f segment -segment_time 600 -segment_wrap 9 -reset_timestamps 1 `
  
  -segment_format_options max_delay=0 C:\Users\Jordan\Videos\FFmpeg\Right\Right%02d.ts

  For one reason or another this command is not transcoding video in real-time, which is a big issue when you’re trying to record not simply convert a file. When I omit one of the two outputs or if I halve the resolution of each input / output everything works in real-time. This would make me believe there is a bottleneck in the system somewhere but when monitoring everything in task manager nothing is even close to capping out (GPU encoder, cpu, ram, and SSD below 30% usage).

  Furthermore when I try recording both streams in one 4K60 video via OBS things work perfectly fine, as in real-time. So I don’t understand how transcoding two 1080p60 streams in FFmpeg would be anymore intensive than one 4K60 stream in OBS... When looking at the GPUs encoding chip usage it shows about 30% for the two 1080p60 streams on FFmpeg and 80% usage for single 4K60 stream in OBS, yet the OBS recording is real-time while the FFmpeg recording is at .6x speed.

  Lastly I run a very similar command at home but instead of two 1080p60 streams I’m doing 2 4K60 streams, a 1080p60 stream, and another 2 audio streams without issue. I do have a GTX 1080 though... however when monitoring usage for the 1050 TI being used in this situation nothing points to a GPU bottlecap.

  Any insight would be greatly appreciated, been going at this for hours now with no clue as to what could be causing this.

• OpenCV VideoWriter doesn't work

  8 janvier 2019, par Laura Muiño

  I’m trying to use opencv videoWriter to get a video file. But I get the following problem :

  >[libx264 @ 0x132b680] broken ffmpeg default settings detected
  
  >[libx264 @ 0x132b680] use an encoding preset (e.g. -vpre medium)
  
  >[libx264 @ 0x132b680] preset usage: -vpre <speed> -vpre <profile>
  
  >[libx264 @ 0x132b680] speed presets are listed in x264 --help
  
  >[libx264 @ 0x132b680] profile is optional; x264 defaults to high
  
  >Could not open codec 'libx264': Unspecified error!!! Output video could not be opened
  
  </profile></speed>

  I do have libx264 in my system, so I guess this last line is just a side effect

  The code i’m trying to run is an example taken from How to write video file in OpenCV 2.4.3 .

  int main (int argc, char *argv[]){
  
  // Load input video
  
  VideoCapture input_cap("testi.mp4");
  
  if (!input_cap.isOpened())
  
  {
  
          std::cout << "!!! Input video could not be opened" << std::endl;
  
          return -1;
  
  }
  
  
  
  // Setup output video
  
  cv::VideoWriter output_cap("testo.mp4", 
  
                 input_cap.get(CV_CAP_PROP_FOURCC),
  
                 input_cap.get(CV_CAP_PROP_FPS),
  
                 cv::Size(input_cap.get(CV_CAP_PROP_FRAME_WIDTH),
  
                 input_cap.get(CV_CAP_PROP_FRAME_HEIGHT)));
  
  
  
  if (!output_cap.isOpened())
  
  {
  
          std::cout << "!!! Output video could not be opened" << std::endl;
  
          return -1;
  
  }
  
  
  
  
  
  // Loop to read from input and write to output
  
  cv::Mat frame;
  
  
  
  while (true)
  
  {       
  
      if (!input_cap.read(frame))             
  
          break;
  
  
  
      output_cap.write(frame);
  
  }
  
  
  
  input_cap.release();
  
  output_cap.release();
  
  
  
  return 0;
  
  }

  I found a post with a similar problem How to get stream info from opened file in ffmpeg ? but no one answered correctly yet.
  I’ve found people are told to check if opencv is using old fmmpeg instead of libav, which it isn’t since it’s a fresh build and my ubuntu doesn’t have ffmpeg.