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• Fastest way to extract raw Y' plane data from Y'Cb'Cr encoded video ?

  20 février 2024, par memeko

  I have a use-case where I'm extracting I-Frames from videos and turning them into perceptual hashes for later analysis.

  


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  I'm currently using ffmpeg to do this with a command akin to :

  


  ffmpeg -skip_frame nokey -i 'in%~1.mkv' -vsync vfr -frame_pts true -vf 'keyframes/_Y/out%~1/%%06d.bmp'

  


  and then reading in the data from the resulting images.

  


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  This is a bit wasteful as, to my understanding, ffmpeg does implicit YUV -> RGB colour-space conversion and I'm also needlessly saving intermediate data to disk.

  


  Most modern video codecs utilise chroma subsampling and have frames encoded in a Y'C_bC_r colour-space, where Y' is the luma component, and Cb Cr are the blue-difference, red-difference chroma components.

  


  Which in something like YUV420p used in h.264/h.265 video codecs is encoded as such :

  


  

  


  Where each Y' value is 8 bits long and corresponds to a pixel.

  


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  As I use gray-scale data for generating the perceptual hashes anyway, I was wondering if there is a way to simply grab just the raw Y' values from any given I-Frame into an array and skip all of the unnecessary conversions and extra steps ?

  


  (as the luma component is essentially equivalent to the grayscale data i need for generating hashes)

  


  I came across the -vf 'extractplanes=y' filter in ffmpeg that seems like it might do just that, but according to source :

  


  


  "...what is extracted by 'extractplanes' is not raw data of the (for example) Y plane. Each extracted is converted to grayscale. That is, the converted video data has YUV (or RGB) which is different from the input."

  


  


  which makes it seem like it's touching chroma components and doing some conversion anyway, in testing applying this filter didn't affect the processing time of the I-Frame extraction either.

  


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  My script is currently written in Python, but I am in the process of migrating it to C++, so I would prefer any solutions pertaining to the latter.

  


  ffmpeg seems like the ideal candidate for this task, but I really am looking for whatever solution that would ingest the data fastest, preferably saving directly to RAM, as I'll be processing a large number of video files and discarding I-Frame luma pixel data once a hash has been generated.

  


  I would also like to associate each I-Frame with its corresponding frame number in the video.

  


• Android Video color effect issue using FFMPEG [on hold]

  8 juin 2016, par umesh mishra

  I m facing one problem. when we use library for effect that i have mentioned below video is created only 1/3 of actual video size. please tell me what is issue. and also doesn’t work on marshmallow.
  https://github.com/krazykira/VidEffects/wiki/Permanent-video-effects

• Try out the latest Piwik 3.0.0 beta version : Piwik 3.0.0 is almost here !

  15 novembre 2016, par Matthieu Aubry — Uncategorized

  Dear Piwik community,

  We are excited today to announce our publicly available Piwik 3.0.0 beta 3 release. We have been been working hard behind the scenes on the new 3.0.0 release for almost one year now. We, the passionate team at Piwik, are dedicated to bringing you a new and improved Piwik experience and invite you to join our beta channel to switch to Piwik 3 today !

  Enable the beta release channel

  Ready to enjoy a much faster Piwik experience and the magic of a modern user interface ? Follow the instructions here and you can upgrade to Piwik 3.0.0 beta in just one click.

  Please note that beta versions have a risk of containing bugs so we don’t recommend to use on a production server. If you find and report a bug in a beta version, we will aim to fix it as quickly as possible.

  Premium plugins in Piwik 3

  In the Piwik Marketplace you can discover & download plugins to enrich the functionality of your Piwik, as well as themes to change the look and feel of your Piwik user interface. The Marketplace integration was much improved in this new release, most notably : you can now purchase and download Premium plugins within Piwik !

  Important changes

  The Piwik 3 upgrade comes with some important changes that may require your attention which we detail in this blog post and in the developer changelog.

  The full list of more than 150 changes can be found in the Piwik 3 beta changelogs : beta 1, beta 2, beta 3.

  What to do next

  When you use the Piwik beta channel and if you come across any issues in Piwik such as a bug, feature missing, regression… let us know on our tracker and create a new issue so we can get this sorted.

  As we are in the final days of Piwik 3 development, we are looking forward to your feedback and help testing !

  Welcome to the future of Piwik,

  Happy Analytics !