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• ffmpeg video duration is not equal to duration after hls process

  9 décembre 2022, par Timur Khazhiev

  Problem

  


  For videofile input I preprocess/encode it to libx264. Then I'm trying to cut video into 2 second chunks except last one (last one being < 2 seconds) using hls processing

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  ffmpeg -v error -i video.mp4 -x264-params "keyint=60:min-keyint=60:scenecut=0" 
-hls_time 2 -hls_list_size 0 -hls_segment_filename chunk%03d.ts index.m3u8


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  which follows this problem

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  then looking into index.m3u8 file reveals that sum of all chunks' durations does not add up to original video duration :

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  % ffprobe -loglevel quiet -print_format flat -show_entries format=duration index.m3u8     

format.duration="204.880000"

% ffprobe -loglevel quiet -print_format flat -show_entries format=duration video.mp4 

format.duration="204.892813"


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  Moreover duration of a chunk in index.m3u8 is not the same as in chunk file.

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  % ffprobe -loglevel quiet -print_format flat -show_entries format=duration chunk000.ts

format.duration="2.023222"

% cat index.m3u8
#EXTM3U
#EXT-X-VERSION:3
#EXT-X-TARGETDURATION:2
#EXT-X-MEDIA-SEQUENCE:0
#EXTINF:2.000000,
chunk000.ts
#EXTINF:2.000000,
chunk001.ts
#EXTINF:2.000000,
chunk002.ts
...


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  Misc

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  Used these videos : Me at the zoo and I finally found a useful monorail.

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  OS : macos Monterey 12.3.1 (21E258)

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  ffmpeg version 5.1.2 Copyright (c) 2000-2022 the FFmpeg developers
built with Apple clang version 14.0.0 (clang-1400.0.29.102)
configuration: --prefix=/usr/local/Cellar/ffmpeg/5.1.2 --enable-shared --enable-pthreads --enable-version3 --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libdav1d --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librist --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libspeex --enable-libsoxr --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack --enable-videotoolbox
libavutil      57. 28.100 / 57. 28.100
libavcodec     59. 37.100 / 59. 37.100
libavformat    59. 27.100 / 59. 27.100
libavdevice    59.  7.100 / 59.  7.100
libavfilter     8. 44.100 /  8. 44.100
libswscale      6.  7.100 /  6.  7.100
libswresample   4.  7.100 /  4.  7.100
libpostproc    56.  6.100 / 56.  6.100


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  What I tried

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  • Preprocess/transcode video before proceeding with hls

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  • Force keyframes before proceeding with hls

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  • Use 1, 3, 4 seconds chunks

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  • Use different GOP sizes

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  • -hls_flags split_by_time

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  but it leads to same result or very unequal chunks

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  Questions

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  1. Is it ok or I'm missing something ?

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  2. If not, what parameters/options should I use to force chunks to be precisely 2 seconds ?

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• Bash : bash script to download trimmed mp3 from youtube url

  25 août 2017, par Bhishan Poudel

  I would like to download the initially x seconds trimmed mp3 from a video url of youtube.
  I found that youtube-dl can download the video from youtube to local machine. But, when I looked at the man pages of youtube-dl, I could not find any trim options.

  So I tried to use the ffmpeg to trim downloaded mp3 file.
  Instead of doing this is two steps, I like to write one bash script which does the same thing.
  My attempt is given below.

  However, I was stuck at one place :
  "HOW TO GET THE VARIABLE NAME OF OUTPUT MP3 FILE FROM YOUTUBE-DL ?"
  The script is given below :

  # trim initial x seconds of mp3 file
  
  # e.g. mytrim https://www.youtube.com/watch?v=dD5RgCf1hrI 30
  
  function mytrim() {
  
      youtube-dl --extract-audio --embed-thumbnail --audio-format mp3 -o "%(title)s.%(ext)s" $1
  
      ffmpeg -ss $2 -i $OUTPUT_MP3 -acodec copy -y temp.mp3
  
      mv temp.mp3 $OUTPUT_MP3
  
      }

  How to get the variable value $OUTPUT_MP3 ?
  echo "%(title)s.%(ext)s" gives the verbatim output, does not give the output filename.

  How could we make the script work ?

  The help will be appreciated.

• Bash : bash script to download trimmed mp3 from youtube url

  23 février 2017, par Bhishan Poudel

  I would like to download the initially x seconds trimmed mp3 from a video url of youtube.
  I found that youtube-dl can download the video from youtube to local machine. But, when I looked at the man pages of youtube-dl, I could not find any trim options.

  So I tried to use the ffmpeg to trim downloaded mp3 file.
  Instead of doing this is two steps, I like to write one bash script which does the same thing.
  My attempt is given below.

  However, I was stuck at one place :
  "HOW TO GET THE VARIABLE NAME OF OUTPUT MP3 FILE FROM YOUTUBE-DL ?"
  The script is given below :

  # trim initial x seconds of mp3 file
  
  # e.g. mytrim https://www.youtube.com/watch?v=dD5RgCf1hrI 30
  
  function mytrim() {
  
      youtube-dl --extract-audio --embed-thumbnail --audio-format mp3 -o "%(title)s.%(ext)s" $1
  
      ffmpeg -ss $2 -i $OUTPUT_MP3 -acodec copy -y temp.mp3
  
      mv temp.mp3 $OUTPUT_MP3
  
      }

  How to get the variable value $OUTPUT_MP3 ?
  echo "%(title)s.%(ext)s" gives the verbatim output, does not give the output filename.

  How could we make the script work ?

  The help will be appreciated.