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• Mjpeg recording with FFMPEG preserving time information

  14 septembre 2012, par Muhammad Adeel Zahid

  I am recording the MJPEG video from an IP camera and saving it to a file but the problem is that file's duration is way smaller than the actual recording time. Its around 9 seconds video for 2 minutes recording. I tried following commands in order

  ffmpeg -f mjpeg -r 8 -i http://c-cam.uchicago.edu/mjpg/video.mjpg -vcodec mpeg4 -b 1000000 -r 8 video_file.avi 

  Then I omitted the most of the flags and tried like this

  ffmpeg -f mjpeg -i http://c-cam.uchicago.edu/mjpg/video.mjpg video_file.avi

  But the problem is that the duration of recorded file is 9 seconds where as the actual recording time is around 2 minutes. I finally tried setpts filter that is supposed to insert the timestamps. The command is as follows

  ffmpeg -f mjpeg -i http://c-cam.uchicago.edu/mjpg/video.mjpg -vf "setpts=1*PTS" video_file.avi

  But result was still the same. Recording time was way more than video duration. How can I add presentational time stamps when recording from mjpeg source using ffmpeg ?

• Using ffmpeg to extract webvtt (SRT) subtitles

  4 mars 2021, par user15332104

  I am trying to extract SRT subtitles from the movies online with use of ffmpeg.
Unfortunately transmission drops after some segments, and there is no output SRT file

  


  Any advice which switch use ? Anything else than ffmpeg would serve the purpose here ?

  


  ffmpeg -i "https://rts-vod-amd.akamaized.net/ch/hls/11997514/8f3c162a-6224-3cac-8f47-788ef9fd24dc/index-f7.m3u8" -scodec srt berry_subs.srt

  


  (Actual movie : https://www.rts.ch/play/tv/telefilm/video/meurtres-en-berry?urn=urn:rts:video:11997514)

  


  ffmpeg -i "https://rts-vod-amd.akamaized.net/ch/hls/12003885/cd6616a8-b1bc-39f8-b900-53ab628eba9e/index-f7.m3u8" -scodec srt mlh_subs.srt

  


  (Actual movie : https://www.rts.ch/play/tv/telefilm/video/meurtres-a-mulhouse?urn=urn:rts:video:12003885 )

  


• softsubs with attached fonts to hardsubs

  4 septembre 2013, par XZS

  When I have softsubs (subtitle saved as *.ass or other text format) with fonts attached in the video file, I use a pipeline like this to encode them to hardsubs (subs burnt into the video image).

  First, extract the subtitles from the container.

  ffmpeg -i video.mkv -map 0:s sub.ass

  Then, install the fonts locally, so that fontconfig finds them there when encoding. To be able to clean up more easily later on, put them in a directory.

  mkdir ~/.fonts/tmp
  
  cd ~/.fonts/tmp
  
  ffmpeg -dump_attachment:t '' -i /path/to/video.mkv
  
  cd -  # back to origin

  The actual encoding follows.

  ffmpeg -i video.mkv -filter:v ass=sub.ass \
  
    [some other encoding & quality options] \
  
    -map 0:v -map 0:a out.mkv  # actual encoding

  And some cleanup at the end.

  rm -r sub.ass ~/.fonts/tmp  # clean up

  A lengthy and messy process with many temporary files, particularly because of fontconfig, which only looks for fonts into some very certain directories. Is there a possibility to omit subtitle or font extraction and use them directly from the container, perhaps with a complex filtergraph.

  Or can fontconfig at least be directed to look for fonts in the current working directory just for the encoding call ? I was thinking of something along the lines of

  FONTCONFIG_SEARCH_PATH=.:$FONTCONFIG_SEARCH_PATH ffmpeg ...

  but could only find configuration files that change the fontconfig search path for all applications.