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• Using ffmpeg to encode web dash and audio drift

  1er octobre 2016, par John Joske

  I’m trying to use ffmpeg to create webm-dash encoded files from a usb web cam. Adapted from this example http://wiki.webmproject.org/adaptive-streaming/instructions-to-do-webm-live-streaming-via-dash

  I have managed to get something nearly works with the following command :

  ffmpeg -f video4linux2 -framerate 30 -s 640x360 -i /dev/video0
  -thread_queue_size 512 -f alsa -ar 44100 -ac 2 -i hw:2 -map 0:0 -pix_fmt yuv420p -c:v libvpx-vp9 -s 640x360 -keyint_min 60 -g 60 -speed 6 -tile-columns 4 -frame-parallel
  1 -threads 8 -static-thresh 0 -max-intra-rate 300 -deadline realtime
  -lag-in-frames 0 -error-resilient 1 -f webm_chunk -header video_360.hdr" -chunk_start_index 1 video_360_%d.chk -map 1:0 -c:a libvorbis -b:a 128k -ar 44100
  -f webm_chunk -copytb 1 -audio_chunk_duration 2000 -header video_171.hdr -chunk_start_index 1 video_171_%d.chk

  However over a period of time the audio chunks slowly get behind the video chunks, can anyone suggest a way to ensure they stay the same.

• Does 'keyint infinite' improve overall compression with crf and mb-tree ?

  23 avril 2012, par HitomiTenshi

  After reading what intra-refresh does, I kinda got confused. I'm encoding for YouTube and YouTube will re-encode the video-file anyways, so I thought "why not removing all these heavy IDR-frames ?" I just want to compress my video as hard as possible, enabling everything that could help me getting a lower filesize, but still maintaining a high quality.

  I used to test around stuff with lossless QP encoding, but the only thing I could max out was the merange. Here is a paste of my x264 settings : Pastebin.

  I want to achieve highest compression while maintaining visually lossless quality. (using crf values around 10 - 13, and merange 32)

  Could anyone give me advice on how to compress my video super hard (without touching the crf value !). I also want to know if it's true, that keyint infinite reduces overall compression.

• parallel ffmpeg filter complex pipelines

  3 septembre 2021, par Paul Eppner

  Is there a possibility to run ffmpeg filter_complex filter in parallel pipelines ?
On the page http://trac.ffmpeg.org/wiki/Creating%20multiple%20outputs you can find an example under the heading "One filtering instance per each output". However, the filters mentioned there (boxblur,negate,yadif) are executed one after the other, although they could also all be executed simultaneously. I have quite complex filters and therefore long delays when the filters are executed one after the other.

  


  I hope there is another solution.
Cheers

  


  ---

  


  A few hours later I realised that the delay was probably not due to the pipeline, but to the analysis of the imports. However, I then only use the video and audio of the 1st stream. nevertheless, the delay time is then enormously high. Are there any ideas on how I can prevent this delay ?

  


      -i "rtmp://127.0.0.1:1935/$app/$name-de" \
    -i "rtmp://127.0.0.1:1935/$app/$name-en" \
    -i "rtmp://127.0.0.1:1935/$app/$name-fr" \
    -i "rtmp://127.0.0.1:1935/$app/$name-es" \
    -i "rtmp://127.0.0.1:1935/$app/$name-it" \
    -i "rtmp://127.0.0.1:1935/$app/$name-de" \
    -i "rtmp://127.0.0.1:1935/$app/$name-en" \
    -i "rtmp://127.0.0.1:1935/$app/$name-fr" \
    -i "rtmp://127.0.0.1:1935/$app/$name-es" \
    -i "rtmp://127.0.0.1:1935/$app/$name-it" \
    -i "rtmp://127.0.0.1:1935/$app/$name-de" \
    -i "rtmp://127.0.0.1:1935/$app/$name-en" \
    -i "rtmp://127.0.0.1:1935/$app/$name-fr" \
    -i "rtmp://127.0.0.1:1935/$app/$name-es" \
    -i "rtmp://127.0.0.1:1935/$app/$name-it" \
    -vsync -1 \
    -map 0:v -c:v:0 copy \
    -map 0:a \
    -c:a aac -ar 48000 \...```