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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 ?

  


• Anomalie #2661 (Fermé) : fusion ?

  16 avril 2012, par Ben .

  contexte : la page archives est presque vide : http://www.spip-blog.net/spip.php?page=archive sur le blog de b_b en spip2 / mysql la boucle MONTH> retourne SELECT articles.date, MONTH(date) FROM spip_articles AS `articles` WHERE (articles.statut = ’publie’) AND (articles.date en spip3 sur (...)

• ffmpeg : Variable based overlay

  25 juin 2018, par Hoofamon

  I am building a video from a collection of images, currently I am just using the ffmpeg command line tool for this :

  ffmpeg -framerate 60 -pattern_type glob -i "${photoDir}/archives/*.jpg" -c:v libx264 -pix_fmt yuv420p $movieDir/vidout.mp4

  I would like to overlay a string value on the video that would change for each input file image, it would be the name of that file with some slight changes. Is this something that is possible with the commandline utility and a script, or would I need to write a program using the ffmpeg lib ?

  Thank you