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• avfilter/vf_transpose_vulkan : add clock and cclock option

  10 décembre 2021, par Wu Jianhua

  avfilter/vf_transpose_vulkan : add clock and cclock option
  The following command is on how to apply cclock option :
  ffmpeg -init_hw_device vulkan -i input.264 -vf \
  
  hwupload=extra_hw_frames=16,transpose_vulkan=dir=cclock,hwdownload,format=yuv420p \
  
  output.264
  The following command is on how to apply clock_flip option :
  ffmpeg -init_hw_device vulkan -i input.264 -vf \
  
  hwupload=extra_hw_frames=16,transpose_vulkan=dir=clock_flip,hwdownload,format=yuv420p \
  
  output.264
  The following command is on how to apply clock option :
  ffmpeg -init_hw_device vulkan -i input.264 -vf \
  
  hwupload=extra_hw_frames=16,transpose_vulkan=dir=clock,hwdownload,format=yuv420p \
  
  output.264
  Signed-off-by : Wu Jianhua <jianhua.wu@intel.com>
  

  • [DH] libavfilter/vf_transpose_vulkan.c

• How to overlay clock with real-time in screen recording using ffmpeg for Sharex open source ?

  1er septembre 2022, par calengineer

  I currently have ShareX and using the following command but the clock with real time is not being added and the video gets considerably cut. A 30 second video turns out to be a 4 second video.

  


  -hide_banner -f dshow -thread_queue_size 1024 -rtbufsize 256M -audio_buffer_size 80 -framerate 30 -i video="screen-capture-recorder":audio="virtual-audio-capturer" -f dshow -i audio="Microphone (HyperX QuadCast S)" -filter_complex amix=inputs=2:duration=longest -vf "drawtext=fontfile=/usr/share/fonts/dejavu/DejaVuSans-Bold.ttf: \ text='%{localtime\:%T}': fontcolor=white@0.8: x=7: y=700" -c:v libx264 -r 30 -preset ultrafast -tune zerolatency -crf 28 -pix_fmt yuv420p -movflags +faststart -c:a aac -ac 2 -b:a 128k -y "output.mp4"


  


• Calculating PCR (Program clock reference) in MPEG2 Transport stream

  1er octobre 2024, par Tomislav Timic

  i am implementing transcoder and packager for abr protocols (HLS/DASH), and also udp mutlicast as output option. I am currently finishing multiplexing of mpeg 2 transport streams, but i do not really understand how should pcr work, how should I calculate it, I have pts/dts values, is there some formula to derive pcr from pts and/or dts ? When i do tsdump from tsduck with ffmpeg output they have around +100ms PCR delay on PTS.

  


  I found some calculations like this :

  


  (int64_t) ((8.0 * (packetsWritten * TS_PACKET_LENGTH + offset) / tsMuxrate) * TS_CLOCK + 0.5) + pcrStart


  


  But it does not match ffmpeg calculation. When i do like this :

  


  base = (int64_t) packet->dts - (int64_t) (SYSTEM_CLOCK_FREQ_90kHz * 0.1);


  


  It has +100ms delay from PTS. But it is hardcoded.