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• How to merge a segmented webvtt subtitle file and output a single srt file ?

  24 janvier 2019, par Dobbelina

  How to merge a segmented webvtt subtitle file and output a single srt file ?,
  m3u8 looks like this example :

  #EXTM3U
  
  #EXT-X-VERSION:4
  
  #EXT-X-PLAYLIST-TYPE:VOD
  
  #EXT-X-MEDIA-SEQUENCE:1
  
  #EXT-X-INDEPENDENT-SEGMENTS
  
  #EXT-X-TARGETDURATION:4
  
  #USP-X-TIMESTAMP-MAP:MPEGTS=900000,LOCAL=1970-01-01T00:00:00Z
  
  #EXTINF:4, no desc
  
  0ghzi1b2cz5(11792107_ISMUSP)-textstream_swe=2000-1.webvtt
  
  #EXTINF:4, no desc
  
  0ghzi1b2cz5(11792107_ISMUSP)-textstream_swe=2000-2.webvtt
  
  #EXTINF:4, no desc
  
  0ghzi1b2cz5(11792107_ISMUSP)-textstream_swe=2000-3.webvtt
  
  #EXTINF:4, no desc
  
  0ghzi1b2cz5(11792107_ISMUSP)-textstream_swe=2000-4.webvtt
  
  #EXTINF:4, no desc
  
  0ghzi1b2cz5(11792107_ISMUSP)-textstream_swe=2000-5.webvtt
  
  #EXTINF:4, no desc
  
  0ghzi1b2cz5(11792107_ISMUSP)-textstream_swe=2000-6.webvtt
  
  #EXT-X-ENDLIST

  I noticed that each segment is not synchronized/cued against total playing time, but against the individual ts segments.
  If ffmpeg could be used to do this, what magic input do i need to give it ?

  A single correctly cued vtt file would work to.
  Thanks for any replies you lovely people !

• How to losslessly compress a sequence of slowly-changing images into a video ?

  26 juillet 2023, par Claude C

  I have a sequence of jpeg images captured like a timelapse, with the same dimension and changing slowly in order. I want to compress the size of the whole sequence while still able to recover each individual image with their raw pixel information unchanged.

  


  I googled and found that a possible solution is to compress it into a video, which exploits the strong temporal correlation (inter-frame redundancy) between consecutive frames, as suggested here. I tried ffmpeg libx264 but none of the option combinations seem to preserve frame quality and compress total size at the same time (-crf 0 keeps the quality but the size of the video is even larger than the input sequence).

  


  So my questions is,

  


  

  • What is the correct way to losslessly compress a sequence of slowly-changing images ?

  


  


  I can accept using softwares other than ffmpeg (as long as it is on windows or linux), doing color space conversion on raw images (if necessary). It is OK if a the compression is done without converting to videos. Thank you.

  


• Linking PHP audio and video uploads to FFMPEG on a linux server

  21 janvier 2016, par user5399793

  I host a site on a Linux server that I built with php where I am able to upload audio files in one section and video files to another. Each section uses php to upload a single audio file and a single video file. Each upload is assigned a unique filename so they can be viewed separately on an individual page where the uploader can post comments about their audio or video. I want to be able to allow musicians and performers in the local area display their work. The site works, but large video files do not upload and my audio player only plays a few formats, and I like to convert them all to mp3’s. I installed ffmpeg on my linux server to help me with this and am able to connect to it with my terminal. My question is how do I get ffmpeg to interface with my uploaded php files. For example, as the user uploads an audio file, can I have ffmpeg convert it while it’s uploading, or do I need to set up a temporary folder for uploads, store it there, then have ffmpeg compress the file, convert it to a specific format and save it in another folder ? I would prefer to have it compress and change the format while it’s uploading so as not to use server space, but if this is not the way ffmpeg works, then I don’t have a choice. Any help would be appreciated.