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    25 avril 2011, par

    MediaSPIP 0.1 beta is the first version of MediaSPIP proclaimed as "usable".
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    To get a working installation, you must manually install all-software dependencies on the server.
    If you want to use this archive for an installation in "farm mode", you will also need to proceed to other manual (...)

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    5 mars 2010, par

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    10 mars 2010, par

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Sur d’autres sites (10545)

  • FFmpeg segmentation and transcoding missing frames

    15 décembre 2022, par Davidec0018

    I code videos for hobbies and have a decent understanding of ffmpeg and mkvmerge. I prefer to encode video when my computer is on for other things as well, so I recently looked for a way that I could resume encoding after the computer was turned off.

    


    I tried a virtual machine, saving the whole state and it seems to work very well, but the performance is very slow and with the same settings the encoding time is much longer than normal.

    


    I then tried to divide the starting video into several segments, so as to resume from the appropriate segment after restarting the computer.

    


    I tried to do this with ffmpeg :

    


    ffmpeg -i input -map 0:v:0 -c copy -f segment -segment_time 300 -reset_timestamps 1 segment%03d.mkv


    


    But also with the mkvtoolnix gui.

    


    Both operations provide an excellent result.Trying to merge the segments into one video, with ffconcat or mkvtoolnix the result is perfect.

    


    The problem arises when segments are encoded. I use a simple script based on slow preset for every segment in loop (I use both windows and linux) :

    


    ffmpeg -i input.mkv -threads 0 -map 0 -c:a copy -c:s copy -preset slow -pix_fmt yuv420p10le -c:v libx265 -x265-params crf=18:bframes=8:aq-mode=2:aq-strength=1.0 output.mkv


    


    Putting them together in the same way, the video also looks quite good, and with the naked eye you don't notice the passage of the various segments, but analyzing them with ffmpeg I notice that the individual segments have slightly shorter durations and a different number of frames, even 2 or 3 less. When putting together very long videos, you notice even 2 seconds of difference with the original, which also causes the audio and subtitles to go into desynch.

    


    I know the problem has to do with keyframes, timestamps and stuff like that. But I don't understand why. FFmpeg, as well as mkvmerge should split the video exactly where the keyframes are, about 300 seconds apart, so as not to mess up the video structure and allow for good encoding and reassembling.

    


    The problem is just encoding with ffmpeg that removes some frames from the original segments. Sometimes I noticed during the encoding of some segments the following error code, or maybe warning, because the encoding worked anyway :

    


    [hevc @ 0x55758bf92dc0] First slice in a frame missing.
    Last message repeated 6 times
[hevc @ 0x55758c2000c0] First slice in a frame missing.


    


    I've read every discussion about it on the net, I've tried to segment both with mp4 and mkv format, with and without audio, but the problem remains. Where am I doing wrong ?

    


  • aarch64 : vp9itxfm : Do separate functions for half/quarter idct16 and idct32

    22 novembre 2016, par Martin Storsjö
    aarch64 : vp9itxfm : Do separate functions for half/quarter idct16 and idct32

    This work is sponsored by, and copyright, Google.
    

    This avoids loading and calculating coefficients that we know will
    
be zero, and avoids filling the temp buffer with zeros in places
    
where we know the second pass won’t read.
    

    This gives a pretty substantial speedup for the smaller subpartitions.
    

    The code size increases from 14740 bytes to 24292 bytes.
    

    The idct16/32_end macros are moved above the individual functions ; the
    
instructions themselves are unchanged, but since new functions are added
    
at the same place where the code is moved from, the diff looks rather
    
messy.
    

    Before :
    
vp9_inv_dct_dct_16x16_sub1_add_neon :     236.7
    
vp9_inv_dct_dct_16x16_sub2_add_neon :    1051.0
    
vp9_inv_dct_dct_16x16_sub4_add_neon :    1051.0
    
vp9_inv_dct_dct_16x16_sub8_add_neon :    1051.0
    
vp9_inv_dct_dct_16x16_sub12_add_neon :   1387.4
    
vp9_inv_dct_dct_16x16_sub16_add_neon :   1387.6
    
vp9_inv_dct_dct_32x32_sub1_add_neon :     554.1
    
vp9_inv_dct_dct_32x32_sub2_add_neon :    5198.5
    
vp9_inv_dct_dct_32x32_sub4_add_neon :    5198.6
    
vp9_inv_dct_dct_32x32_sub8_add_neon :    5196.3
    
vp9_inv_dct_dct_32x32_sub12_add_neon :   6183.4
    
vp9_inv_dct_dct_32x32_sub16_add_neon :   6174.3
    
vp9_inv_dct_dct_32x32_sub20_add_neon :   7151.4
    
vp9_inv_dct_dct_32x32_sub24_add_neon :   7145.3
    
vp9_inv_dct_dct_32x32_sub28_add_neon :   8119.3
    
vp9_inv_dct_dct_32x32_sub32_add_neon :   8118.7
    

    After :
    
vp9_inv_dct_dct_16x16_sub1_add_neon :     236.7
    
vp9_inv_dct_dct_16x16_sub2_add_neon :     640.8
    
vp9_inv_dct_dct_16x16_sub4_add_neon :     639.0
    
vp9_inv_dct_dct_16x16_sub8_add_neon :     842.0
    
vp9_inv_dct_dct_16x16_sub12_add_neon :   1388.3
    
vp9_inv_dct_dct_16x16_sub16_add_neon :   1389.3
    
vp9_inv_dct_dct_32x32_sub1_add_neon :     554.1
    
vp9_inv_dct_dct_32x32_sub2_add_neon :    3685.5
    
vp9_inv_dct_dct_32x32_sub4_add_neon :    3685.1
    
vp9_inv_dct_dct_32x32_sub8_add_neon :    3684.4
    
vp9_inv_dct_dct_32x32_sub12_add_neon :   5312.2
    
vp9_inv_dct_dct_32x32_sub16_add_neon :   5315.4
    
vp9_inv_dct_dct_32x32_sub20_add_neon :   7154.9
    
vp9_inv_dct_dct_32x32_sub24_add_neon :   7154.5
    
vp9_inv_dct_dct_32x32_sub28_add_neon :   8126.6
    
vp9_inv_dct_dct_32x32_sub32_add_neon :   8127.2
    

    Signed-off-by : Martin Storsjö <martin@martin.st>
    • [DBH] libavcodec/aarch64/vp9itxfm_neon.S

  • build : rename version.h to libavutil/ffversion.h

    29 novembre 2013, par Timothy Gu
    build : rename version.h to libavutil/ffversion.h

    Also the libavutil/ffversion.h will be installed.
    

    Rationale :
    
* Applications might want to know FFmpeg’s version besides the individual
    
  libraries’.
    
* Avoids file name clash between FFmpeg’s ./version.h and lib*/version.h when
    
  a library source file includes both and is compiled on an out-of-tree build.
    

    Fixes #1769.
    

    Signed-off-by : Timothy Gu <timothygu99@gmail.com>
    
Reviewed-by : James Almer <jamrial@gmail.com>
    
Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
    • [DH] .gitignore
    • [DH] Makefile
    • [DH] cmdutils.c
    • [DH] doc/APIchanges
    • [DH] ffprobe.c
    • [DH] libavutil/Makefile
    • [DH] libavutil/version.h

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