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• aacenc_tns : rework coefficient quantization and filter application

  1er septembre 2015, par Rostislav Pehlivanov

  aacenc_tns : rework coefficient quantization and filter application
  This commit reworks the TNS implementation to a hybrid between what
  
  the specifications say, what the decoder does and what’s the best
  
  thing to do.
  The filter application function was copied from the decoder and
  
  modified such that it applies the inverse AR filter to the
  
  coefficients. The LPC coefficients themselves are fed into the
  
  same quantization expression that the specifications say should
  
  be used however further processing is not done, instead they’re
  
  converted to the form that the decoder expects them to be in
  
  and are sent off to the compute_lpc_coeffs function exactly the
  
  way the decoder does. This function does all conversions and will
  
  return the exact coefficients that the decoder will generate, which
  
  are then applied to the coefficients.
  
  Having the exact same coefficients on both the encoder and decoder
  
  is a must since otherwise the entire sfb’s over which the filter
  
  is applied will be attenuated.
  Despite this major rework, TNS might not work fine on some audio
  
  types at very low bitrates (e.g. sub 90kbps) as it can attenuate
  
  some coefficients too much. Users are advised to experiment with
  
  TNS at higher bitrates if they wish to use this tool or simply
  
  wait for the implementation to be improved.
  Signed-off-by : Rostislav Pehlivanov <atomnuker@gmail.com>
  

  • [DH] libavcodec/aacenc.c
  • [DH] libavcodec/aacenc.h
  • [DH] libavcodec/aacenc_tns.c
  • [DH] libavcodec/aacenc_tns.h

• lavfi : add showwavespic filter

  24 décembre 2014, par Clément Bœsch

  lavfi : add showwavespic filter
  This is a variant of showwaves. It is implemented as a different filter
  
  so that the user is not allowed to use meaningless options which belong
  
  to showwaves (such as rate).
  Major edits done by Stefano Sabatini, from a patch by ubitux.
  See thread :
  
  From : Clément Bœsch <u@pkh.me>
  
  To : ffmpeg-devel@ffmpeg.org
  
  Date : Wed, 24 Dec 2014 15:03:26 +0100
  
  Subject : [FFmpeg-devel] [PATCH] avfilter/showwaves : add single_pic option
  

  • [DH] Changelog
  • [DH] doc/filters.texi
  • [DH] libavfilter/Makefile
  • [DH] libavfilter/allfilters.c
  • [DH] libavfilter/avf_showwaves.c
  • [DH] libavfilter/version.h

• Android, fast video processing

  27 avril 2016, par Ilja Kosynkin

  I have troubles in my current project which requires video processing. Basically crop function (video should be squared), trimming (video shouldn’t be longer than 30 seconds) and quality reduction (bitrate should be equal 713K).
  I’ve succesfully embedded FFmpeg into application, all functions are working quite fine except one major detail - processing as per my boss is taking too long time. For video that have around 52 MB for 36 seconds it’s taking 50 seconds to perforn all the operations (I’m trimming video to 30 seconds before any other operation obviously). The problem is that on parallel project on iOS video processing takes like 10-15 seconds for greater files. I assume that it’s related to fact that they’re using Apple QuickTime format which obviusly was developed by Apple so it’s not surprising that it’s working quite fast.
  So well, it was introduction, now my question : is there any way for Android to process any video in any quality (for now we can assume that all videos are in h264) in time of 10-15 seconds (not more then in 30 seconds, as my boss said) ? Some alternative to FFmpeg, that can perform operations faster ? I’nm pretty sure that there is no possibility to perform such work in a such short time, since I already feel like I searched thought while Internet, but I want to make sure that there is really no possibility to do such work. If anyone can provide me links to solution more faster than FFmpeg or confirm that there is no such solution, I will be very gratefull.

  Update
  Thanks to Alex Cohn I’ve resolved this with MediaCodec. After a while, I got 20 seconds processing on 52MB video with cropping to square and lowering bitrate. For any future Googlers out of here I can suggest to take a look at this respository :
  Many stuff about MediaCodec
  and more precisely at this file : Extract, edit and encode again, video and audio