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Sur d’autres sites (5771)

  • ffmpeg : How to replace a series of frames with a series of image files ?

    14 septembre 2020, par Arnon Weinberg

    Given a video file, start and end timestamps, there is a known number of frames between those timestamps in the video file, and I have an equal number of .png files in a directory to replace them with. The .png files are sorted as 001.png ... NNN.png. How would I go about updating the video file with the replacement frames using ffmpeg ?

    


    This is a followup to using ffmpeg to replace a single frame based on timestamp, but I'm asking about replacing multiple sequential frames based on 2 timestamps.

    


    Presumably something like :

    


    ffmpeg -i input.mp4 -i %3d.png -filter_complex "something including the timestamps 4.40,5.20" -c:a copy output.mp4


    


    I would also be okay with using frame numbers instead of timestamps if that makes things easier, and it's reasonable if start and end frames must be keyframes.

    


    Background :

    


    Many machine learning algorithms for video processing use ffmpeg to extract specific scenes from videos based on start and end timestamps, dump them into a sequence of .png files, process them in some way (denoise, deblur, colorize, annotate, inpainting, etc), and output the results into an equal number of .png files. The output frames are usually assembled into a new video file, but I would like instead to update the source video file so as to preserve audio, unedited video, and other video properties (fps, keyframes, etc).

    


    This approach will not work as-is for some categories of video processing algorithms. For example, interpolation results in more frames than were originally extracted, and upscaling results in higher-resolution images. As such, I would appreciate an explanation of any solution so that I can adapt it for such cases (or I will ask separate questions for those).

    


  • fftools/ffmpeg_filter : compute input trim start/end in demuxer

    13 février 2024, par Anton Khirnov
    fftools/ffmpeg_filter : compute input trim start/end in demuxer

    The computation is based on demuxer properties, so that is the more
    
appropriate place for it. Filter code just receives the desired
    
start time/duration.
    • [DH] fftools/ffmpeg.h
    • [DH] fftools/ffmpeg_demux.c
    • [DH] fftools/ffmpeg_filter.c

  • lavc : Introduce AVCodec internal capabilities

    11 mars 2015, par Vittorio Giovara
    lavc : Introduce AVCodec internal capabilities

    This field is designed for marking codec properties useful to lavc internals.
    
Two internal capabilities are added :
    
 - FF_CODEC_CAP_INIT_THREADSAFE : codec can be opened without locks ;
    
 - FF_CODEC_CAP_INIT_CLEANUP : codec frees memory if initialization fails.
    • [DH] libavcodec/avcodec.h
    • [DH] libavcodec/internal.h
    • [DH] libavcodec/utils.c

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