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• How to save ffmpeg segmets to disk immediately with sub-second intervals ?

  20 octobre 2023, par amfast

  I'm trying to record video on a raspberry and have it save as much as possible (sub-second resolution) in case of a power cutoff.

  


  I use -f segment to save the encoded stream in 100ms segments with the hope that all but the interrupted (by power cutoff) segment will be saved in memory. Unfortunately, when cutting off power, all the destination files (output_0001.mp4, output_0002.mp4, ...) are created, but empty.

  


  To save the files to disk immediately, I added the -strftime 1 option that allows formatting the output filename as time. It seems weird that this is the (only ?) way to trigger immediate saving of files, but it works - untill I try to have segments smaller than 1 second. The problem seems to be that the format string %d, that previously added a sequence number in my output filenames, now represents "day" (i.e. date) and the smallest resolution time format string is %S for second. I saw %f suggested somewhere for smaller resolutions, but it only prints "%f".

  


  The result is that the segmentation part of ffmpeg does create 100ms segments and save them to disk immediately, but the strftime feature gives the output files names that only change every second, so all the interim files are overwritten.

  


  Example of the failing command below. Without the -strftime option this creates nice segments, but does not save them to disk immediately.

  


  libcamera-vid --flush \
    --framerate ${FRAMERATE} \
    --width ${WIDTH} \
    --height ${HEIGHT} \
    -n \
    -t ${TIMEOUT} \
    --codec yuv420 \
    -o - | 
ffmpeg \
    -fflags nobuffer \
    -strict experimental \
    -loglevel debug \
    -flags low_delay \
    -f rawvideo \
    -pix_fmt yuv420p \
    -s:v ${WIDTH}x${HEIGHT} \
    -r ${FRAMERATE} \
    -i - \
    -c:v h264_v4l2m2m \
    -f segment \
    -segment_time 0.1 \
    -segment_format mp4 \
    -reset_timestamps 1 \
    -strftime 1 \
    -b:v ${ENCODING_BITRATE} \
    -g 1 \
    "output_%04d.mp4"


  


  Question :
  
Is there another way besides -strftime to trigger immediate saving ? Or is there a mechanism to feed finer resolution format strings to the output filename ?

  


• Offline tracking in Matomo JavaScript Tracker – We need your feedback

  16 octobre 2020, par Matomo Core Team — Development, Uncategorized

  As part of our Matomo 4 release we are working on adding support for offline tracking using service workers (SW) and IndexedDB. An early version of this new feature is now available as part of our latest Matomo 4 beta and we now need your feedback to fix any outstanding issues.

  How does it work behind the scenes ?

  • The service worker caches the Matomo JavaScript tracker so if a user becomes offline on subsequent requests the JS tracker will be still loaded.
  • If a user is offline, any tracking request will be put into the local IndexedDB.
  • Once the user becomes online, all requests from the IndexedDB will be retried.

  How do I integrate offline tracking into my website or app ?

  Follow the steps in our FAQ on how to set up offline tracking. 

  We need your feedback

  We’d love to hear your feedback if this new feature is working for you or not. Simply leave a comment on the offline tracking issue and let us know if it worked for you, if something didn’t work, whether you miss any options or any other kind of feedback.

  Are you a service worker or IndexedDB pro ? We’d love if you could help us review our implementation. You can check out the code in the offline tracking pull request. We appreciate any feedback to help us improve this feature !

  Thank you for your help !

• How to make mpv more compatible with ffmpeg filters like minterpolate ?

  1er octobre 2020, par F usedEmacs -con fused

  ffmpeg filter minterpolate (motion interpolation) does not work in MPV.

  



  (Nevertheless the file then is played normally without the minterpolate).

  



  (I researched using search engines and throughout documentation and troubleshooted to make a use of opengl and generally tried everything apart from asking for help and learning to understand more in the source code and I'm not a programmer)…

  



  --gpu-context=angle --gpu-api=opengl also does not make opengl work. (I'm guessing opengl could help from seeing its use in the documentations).

  



  


  Note

  
 


  To get a full list of available video filters, see —vf=help and
 http://ffmpeg.org/ffmpeg-filters.html .

  
 


  Also, keep in mind that most actual filters are available via the
 lavfi wrapper, which gives you access to most of libavfilter's
 filters. This includes all filters that have been ported from MPlayer
 to libavfilter.

  
 


  Most builtin filters are deprecated in some ways, unless they're only
 available in mpv (such as filters which deal with mpv specifics, or
 which are implemented in mpv only).

  
 


  If a filter is not builtin, the lavfi-bridge will be automatically
 tried. This bridge does not support help output, and does not verify
 parameters before the filter is actually used. Although the mpv syntax
 is rather similar to libavfilter's, it's not the same. (Which means
 not everything accepted by vf_lavfi's graph option will be accepted by
 —vf.)

  
 


  You can also prefix the filter name with lavfi- to force the wrapper.
 This is helpful if the filter name collides with a deprecated mpv
 builtin filter. For example —vf=lavfi-scale=args would use
 libavfilter's scale filter over mpv's deprecated builtin one.

  


  



  I expect MPV to play with minterpolate (one of several filters that MPV can use, listed in http://ffmpeg.org/ffmpeg-filters.html) enabled. But this is what happens :

  



  Input : "--vf=lavfi=[minterpolate=fps=60000/1001:mi_mode=mci]"

  



  Output :

  



     cplayer:  (+) Video --vid=1 (*) (h264 1280x720 29.970fps)
   cplayer:  (+) Audio --aid=1 (*) (aac 2ch 44100Hz)
        vd: Using hardware decoding (d3d11va).
    ffmpeg: Impossible to convert between the formats supported by the filter 'mpv_src_in0' and the filter 'auto_scaler_0'
     lavfi: failed to configure the filter graph
        vf: Disabling filter lavfi.00 because it has failed.


  



  (Interesting is also that --gpu-api=opengl does not work (despite that according to specification my—not to brag—HD Graphics 400 Braswell supports its 4.2 version)… And that aresample seems to have no effect too, and with the few audio filters selected playback often doesn't start nor output errors.)