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• Watching a livestream that is being ripped by ffmpeg to disk - file updating problem

  22 mai 2021, par merlin

  I am automatically recording daily tv news with ffmpeg, so I can watch them later.

  


  ffmpeg -i https://mcdn.daserste.de/daserste/de/master.m3u8 -c copy Tagesschau.mkv


  


  This works. But let's say ffmpeg recorded for 2 minutes and I open the currently saved file and begin to watch the video stops after some time.
It doesn't continue playing (but ffmpeg is still recording so there must be more video).

  


  Strange thing is even by closing and reopening the file I don't see the new content. Sometimes I have to wait 1-2 minutes till the new content shows up. But in the file manager I see the file is growing in size continuous.

  


  But when I copy/paste the file e.g. in the same directory and reopen the file I can immediately see the complete video content up to date recorded.

  


  Maybe it has to do with file system write buffer ? I tried on ZFS and ext4 (mounted on a samba share). By copy/paste I "trigger" the file system to update the file content ?

  


  Is there a workaround so when I start watching it will play without stopping ?

  


• ffmpeg : Dynamically set output duration based on sliding text width

  18 janvier 2016, par John Whiteman

  I need to create a smooth ’news ticker’ on a low powered android device. Unfortunately this is impossible at runtime using HTML or native code as there is always some stutter or glitch.

  I’ve created a solution that gives me a smooth result by encoding an mp4 for each message and displaying one video after the other. This is the code I’m using :

  ffmpeg -f lavfi -i color=c=black:s=1280x100 -vf "drawtext=BebasNeue.otf:fontsize=60:fontcolor=white:y=h-line_h-30:x=-(4*n)+1280:text='Hello world'" -t 10 output.mp4

  Problem :
  I need to set the video’s duration dynamically so that the video stops when the text has completed it’s journey from right to left. The messages will be of varying lengths and I need each message to scroll at a constant speed (ie. an mp4 with a longer message would have a longer duration).

  Is this possible via an expression ? If not is there some clever way I can calculate this outside of ffmpeg and pass it to the ’-t’ (duration) parameter ?

  ** Edit **
  To calculate outside of ffmpeg I can do a calculation like video_width + text_width / video_fps (ie. 1280 + 262 / 25) to give me the duration. So now I’m just looking to see if this is possible within the ffmpeg command line itself. t

  Many thanks

• New Sanyo cameras have editing in mind

  13 octobre 2009

  Sanyo has announced some ’A’ revisions to their existing FH1 and HD2000 cameras, which add a new "iFrame" mode. It appears this is an i-frame only h264 mode, at a reduced 960x540 resolution. It’s a very interesting idea - if other manufacturers adopted it as an optional setting, and if NLE manufacturers supported it, it could turn H264 into an edit-friendly format. Right now, editing H264 is hamstrung by the extremely long GOPs and complex interframe relationships. Going to i-frame only makes it essentially a more advanced version of a codec like DV or DVCProHD.

  Interestingly, the bottom of the press release mentions that

  "The iFrame logo and the iFrame symbol are trademarks of Apple Inc."

  That’s news to me. One wonders if Sanyo jumped the gun on a release, or if this is just a format that Apple uses internally in tools like iMovie, which Sanyo has co-opted. I’ll certainly be keeping my eyes open for an Apple announcement about "iFrame."