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• VP8/WebM : Adobe is the key to open video on the Web

  22 mai 2010, par silvia

  Google have today announced the open sourcing of VP8 and the creation of a new media format WebM. Technical Challenges As I predicted earlier, Google had to match VP8 with an audio codec and a container format – their choice was a subpart of the Matroska format and the Vorbis codec. To complete (...)

• FFmpeg - Delay Only Video Stream Of Audio Linked dshow Input

  15 avril 2018, par Nimble

  I’m having a slight issue trying to sync my audio and video up with an acceptable margin of error. Here is my command :

  ffmpeg -y -thread_queue_size 9999 -indexmem 9999 -guess_layout_max 0 -f dshow -video_size 3440x1440 -rtbufsize 2147.48M ^
  
  -framerate 100 -pixel_format nv12 -i video="Video (00 Pro Capture HDMI 4K+)":audio="SPDIF/ADAT (1+2) (RME Fireface UC)" ^
  
  -map 0:0,0:1 -map 0:1 -flags +cgop -force_key_frames expr:gte(t,n_forced*2) -c:v h264_nvenc -preset: llhp -pix_fmt nv12 ^
  
  -b:v 250M -minrate 250M -maxrate 250M -bufsize 250M -c:a aac -ar 44100 -b:a 384k -ac 2 -r 100 -af "aresample=async=250" ^
  
  -vsync 1 -max_muxing_queue_size 9999 -f segment -segment_time 600 -segment_wrap 9 -reset_timestamps 1 ^
  
  C:\Users\djcim\Videos\PC\PC\PC%02d.ts

  My problem is the video comes in slightly ahead of the audio, I can use -itsoffset but then I have to call the video and audio as separate inputs as -itsoffset offsets both audio and video. While this may seem the obvious solution it causes inconsistent audio synchronization if the audio isn’t called with the video. Basically if both audio and video aren’t called at the same time the video can now be ahead or behind with a 2-3 frame margin. When I call them at the same time the video consistently comes in 2 frames ahead of the audio, every time. I just need a way to delay only the video stream without delaying the audio while keeping both audio and video linked from the beginning. I’ve tried this with no luck :

  ffmpeg -y -thread_queue_size 9999 -indexmem 9999 -guess_layout_max 0 -f dshow -video_size 3440x1440 -rtbufsize 2147.48M ^
  
  -framerate 200 -pixel_format nv12 -i video="Video (00 Pro Capture HDMI 4K+)":audio="SPDIF/ADAT (1+2) (RME Fireface UC)" ^
  
  -flags +cgop -force_key_frames expr:gte(t,n_forced*2) -c:v h264_nvenc -preset: llhp -pix_fmt nv12 -b:v 250M ^
  
  -minrate 250M -maxrate 250M -bufsize 250M -c:a aac -ar 44100 -b:a 384k -ac 2 -r 100 ^
  
  -filter_complex "[0:v] setpts=PTS-STARTPTS+.032/TB [v]; [0:a] asetpts=PTS-STARTPTS, aresample=async=250 [a]" -map [v] ^
  
  -map [a] -vsync 1 -max_muxing_queue_size 9999 -f segment -segment_time 600 -segment_wrap 9 -reset_timestamps 1 ^
  
  C:\Users\djcim\Videos\PC\PC\PC%02d.ts

  Just like -itsoffset both video and audio are being delayed. You can delay solely audio with adelay, but there doesn’t seem to be a video delaying equivalent.

  Any help or advice would be greatly appreciated.

• VLC - standard output 'dst=-' stopped working

  2 juin 2020, par gdogg371

  Using VLC 3 I had the following command working perfectly a few months back :

  



  "G:\VLC\vlc" --ffmpeg-hw --avcodec-hw=any dshow:// :dshow-vdev="Video (00 Pro Capture HDMI 4K+)" :dshow-adev="Audio (2- 00 Pro Capture HDMI 4K+)" :dshow-threads=8 :dshow-aspect-ratio=16\:9 :dshow-size="3840x2160" :dshow-pixel_format=yuv444p16le :dshow-tune=film :dshow-preset=lossless :dshow-profile=main10 show-vcodec=hevc_nvenc :dshow-fps=50 :dshow-crf=0 :dshow-acodec=mp4a :dshow-stereo-mode=5 :dshow-force-surround-sound=0 :dshow-ab=128 :dshow-samplerate=44100 :no-dshow-config :live-caching=300 --sout "#transcode{venc=ffmpeg,vcodec=mp2v,threads=8,aspect=16:9,width=3840,height=2160,fps=50,acodec=a52,ab=1500,channels=6,samplerate=48000,soverlay}:standard{access=file,dst=-,mux=ts}"


  



  ...however dst=- suddenly seems to be causing a problem. I get the following error :

  



  -- logger module started --
main: Running vlc with the default interface. Use 'cvlc' to use vlc without interface.
file error: write error: Bad file descriptor
stream_out_standard error: no suitable sout access module for `file/ts://-'
main error: stream chain failed for `transcode{venc=ffmpeg,vcodec=mp2v,threads=8,aspect=16:9,width=3840,height=2160,fps=50,acodec=a52,ab=1500,channels=6,samplerate=48000,soverlay}:standard{access=file,dst=-,mux=ts}'
main error: cannot start stream output instance, aborting
file error: write error: Bad file descriptor
stream_out_standard error: no suitable sout access module for `file/ts://-'
main error: stream chain failed for `transcode{venc=ffmpeg,vcodec=mp2v,threads=8,aspect=16:9,width=3840,height=2160,fps=50,acodec=a52,ab=1500,channels=6,samplerate=48000,soverlay}:standard{access=file,dst=-,mux=ts}'
main error: cannot start stream output instance, aborting
-- logger module stopped --


  



  Previous behaviour observed was that VLC would open and start streaming. The purpose of this exercise is to pipe the VLC output into a PVR called NPVR.

  



  I have tried uninstalling VLC and downloading a fresh install, but I still have the same issue. Any ideas ?