Recherche avancée

Médias (91)

Autres articles (101)

  • Use, discuss, criticize

    13 avril 2011, par

    Talk to people directly involved in MediaSPIP’s development, or to people around you who could use MediaSPIP to share, enhance or develop their creative projects.
    The bigger the community, the more MediaSPIP’s potential will be explored and the faster the software will evolve.
    A discussion list is available for all exchanges between users.

  • Le plugin : Podcasts.

    14 juillet 2010, par

    Le problème du podcasting est à nouveau un problème révélateur de la normalisation des transports de données sur Internet.
    Deux formats intéressants existent : Celui développé par Apple, très axé sur l’utilisation d’iTunes dont la SPEC est ici ; Le format "Media RSS Module" qui est plus "libre" notamment soutenu par Yahoo et le logiciel Miro ;
    Types de fichiers supportés dans les flux
    Le format d’Apple n’autorise que les formats suivants dans ses flux : .mp3 audio/mpeg .m4a audio/x-m4a .mp4 (...)

  • Des sites réalisés avec MediaSPIP

    2 mai 2011, par

    Cette page présente quelques-uns des sites fonctionnant sous MediaSPIP.
    Vous pouvez bien entendu ajouter le votre grâce au formulaire en bas de page.

Sur d’autres sites (5337)

  • Extract frames from a video results in abnormaly more frames for each fps by using ffmpeg

    15 juin 2021, par alanzzz

    I have a job of using ffmpeg to extract the frames averagely from a video, with different fps. I use this command for it.

    


    ffmpeg -i input.mp4 -r specified_fps -q:v 2 image %4d.png

    


    And I have 3 questions about this task.

    


      

    1. What I expect is that if I double the fps, the number of extracted frames will also get doubled. However, that's not the case. Take one of the input videos as an example. I get 2 extra frames for all the sample factors (80 / 158 / 236 / 392 v.s. 78 / 156 / 234 / 390). Does it related to the mechanism of picking/dropping frames when extracting frames from a video？ (credit to @Tom Yan)

      2. 


    


    video info

    


      

    • Duration : 1min18s

      • 


    • Frame rate mode : constant (CFR)

      • 


    • Frame rate : 30.0 FPS

      • 


    • Total number of frames : 2340

      • 


    


    Config setting & results

    


    





    


    


    


    


    


    



    


    


    


    


    


    


    


    


    


    


    


    


    


    


    


    


    


    


    


    


    FPS Actual num of frames correct num of frames
    1 80 78
    2 158 156
    3 236 234
    5 392 390

    


    


      


    1. I check for the output images, the extracted frames for different fps are totally different from each other. In other words, for example, the 1st image for fps=1 is not the same as the 1st image for fps=2. Is that legitimate ? And is it possible for me the get some identical images for different fps ?

      


      2. 


    2. The last problem is that for some videos I use, the difference between the 1st and 2nd image is different from the difference between the 2nd and 3rd. While for the remaining images, the differences become average. To be specific, there is only a slight change from 1st to 2nd frame, while for 2nd to 3rd, 3rd to 4th, and so on, the changes are the same, which is normally distributed according to the specified FPS. I am wondering why such a case happens ? Does it relate to the I-frame, B-frame, P-frame, GOP, or IDR ?

      


      3. 


    


    I am new to this field and cannot find some useful info from other places. I've tried my best to describe my questions clearly. Feel free to leave some comments. Any help would do me a great favor. Thanks in advance !

    


  • lavc/vvc : Remove left shifts of negative values

    20 janvier 2024, par Frank Plowman
    lavc/vvc : Remove left shifts of negative values

    VVC specifies << as arithmetic left shift, i.e. x << y is equivalent to
    
x * pow2(y).  C's << on the other hand has UB if x is negative.  This
    
patch removes all UB resulting from this, mostly by replacing x << y
    
with x * (1 << y), but there are also a couple places where the OOP was
    
changed instead.
    

    Signed-off-by : Frank Plowman <post@frankplowman.com>
    
Signed-off-by : James Almer <jamrial@gmail.com>
    • [DH] libavcodec/vvc/vvc_ctu.c
    • [DH] libavcodec/vvc/vvc_filter.c
    • [DH] libavcodec/vvc/vvc_inter.c
    • [DH] libavcodec/vvc/vvc_inter_template.c
    • [DH] libavcodec/vvc/vvc_mvs.c

  • Merge commit ’98c97994c5b90bdae02accb155eeceeb5224b8ef’

    19 juin 2016, par Clément Bœsch
    Merge commit ’98c97994c5b90bdae02accb155eeceeb5224b8ef’

    * commit ’98c97994c5b90bdae02accb155eeceeb5224b8ef’ :
    
  h264 : decouple extradata parsing from the decoder
    

    Main changes :
    

    - move get_avc_nalsize() inside h264_parser.c and make it use
    
  H264ParseContext instead of H264Context. This helps fixing
    
  fate-flv-demux.
    

    - Also use is_avc/nal_length_size from the H264ParseContext in various
    
  places instead of the H264Context one as that’s the fields now filled
    
  by ff_h264_decode_extradata()
    

    - h264_parse : dont fail decode_extradata_ps() due to nal split failure.
    
  Change by Michael to fix decoding of h264/ref_10.avi.
    

    Merged-by : Clément Bœsch <u@pkh.me>
    
Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
    • [DH] libavcodec/h264.c
    • [DH] libavcodec/h264.h
    • [DH] libavcodec/h264_parse.c
    • [DH] libavcodec/h264_parse.h
    • [DH] libavcodec/h264_parser.c

Navigation