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• swresample/resample : speed up Blackman Nuttall filter

  9 novembre 2015, par Ganesh Ajjanagadde

  swresample/resample : speed up Blackman Nuttall filter
  This may be a slightly surprising optimization, but is actually based on
  
  an understanding of how math libraries compute trigonometric functions.
  
  Explanation is given here so that future development uses libm more effectively
  
  across the codebase.
  All libm’s essentially compute transcendental functions via some kind of
  
  polynomial approximation, be it Taylor-Maclaurin or Chebyshev.
  
  Correction terms are added via polynomial correction factors when needed
  
  to squeeze out the last bits of accuracy. Lookup tables are also
  
  inserted strategically.
  In the case of trigonometric functions, periodicity is exploited via
  
  first doing a range reduction to an interval around zero, and then using
  
  some polynomial approximation.
  This range reduction is the most natural way of doing things - else one
  
  would need polynomials for ranges in different periods which makes no
  
  sense whatsoever.
  To avoid the need for the range reduction, it is helpful to feed in
  
  arguments as close to the origin as possible for the trigonometric
  
  functions. In fact, this also makes sense from an accuracy point of view :
  
  IEEE floating point has far more resolution for small numbers than big ones.
  This patch does this for the Blackman-Nuttall filter, and yields a
  
  non-negligible speedup.
  Sample benchmark (x86-64, Haswell, GNU/Linux)
  
  test : fate-swr-resample-dblp-2626-44100
  
  old :
  
  18893514 decicycles in build_filter (loop 1000),     256 runs,      0 skips
  
  18599863 decicycles in build_filter (loop 1000),     512 runs,      0 skips
  
  18445574 decicycles in build_filter (loop 1000),    1000 runs,     24 skips
  new :
  
  16290697 decicycles in build_filter (loop 1000),     256 runs,      0 skips
  
  16267172 decicycles in build_filter (loop 1000),     512 runs,      0 skips
  
  16251105 decicycles in build_filter (loop 1000),    1000 runs,     24 skips
  Reviewed-by : Michael Niedermayer <michael@niedermayer.cc>
  
  Signed-off-by : Ganesh Ajjanagadde <gajjanagadde@gmail.com>
  

  • [DH] libswresample/resample.c

• What does "Error in the pull function" mean while executing ffmpeg command ?

  8 avril 2022, par Alex Rypun

  I'm trying to generate a video from multiple video sources (https urls).

  


  If I use say 8 video sources it works as expected. But if I need say 30 sources, it starts to work as expected, but at some moment a lot of errors appear.

  


  

  


  I believe the main one is Error in the pull function..

  


  Such a video-source appears in the output file but not a full requested part (e.g., I set trim=0:5, but ffmpeg generates only 3 seconds).

  


  I tried different videos, different cropped parts, loaded sources to aws s3, but can't identify a "bad case", it's reproduced with different options.

  


  My command looks like this :

  


  ffmpeg -y
-i "https://player.vimeo.com/external/399541658.hd.mp4?s=5432956383527af00bb74b41c120bbb84ff3ac5e&profile_id=175&oauth2_token_id=57447761"
...
-i "https://player.vimeo.com/external/464966383.hd.mp4?s=648aa8277259c499f1d05d6330f9922932c080a6&profile_id=175&oauth2_token_id=57447761"
-i "https://test.com/development/videos/dc3c32cf9a194db1bb52/sources/5q5e3j2h57.mp3"
-filter_complex "[0:v]trim=0:5.64,setpts=PTS-STARTPTS,scale=1920x1080,setdar=16/9[v0];[1:v]trim=0:8,setpts=PTS-STARTPTS,scale=1920x1080,setdar=16/9,loop=0:32767[v1]; ... [10:v]trim=0:13,setpts=PTS-STARTPTS,scale=1920x1080,setdar=16/9[v10];[v0] ... [v10] concat=n=11:v=1 [video];[11:a] atrim=0:99.29 [audio]"
-vsync 2 -map [video] -map [audio] output.mp4


  


  When I downloaded all sources to my local machine and tried to use them in the ffmpeg command it worked fine without errors.

  


  Also, I figured out that it depends on the CPU. When I restricted my CPU the errors appeared earlier. And some commands might produce errors with a restricted CPU but finished successfully with no CPU restriction.

  


  As I understand, for some reason, ffmpeg fails to receive a particular part of a file data, but I believe it should retry to receive lost packages (it's https).

  


  And I don't understand, how it could be related to CPU or sources quantity.

  


  By not understanding the core of evil, I can think about 2 ways (both ugly) :

  


  

  1. to download all sources and generate the final video from local files ;

  


  2. to chunk sources, generate intermediate outputs for each chunk (and save locally), and concatenate them into the final one.

  


  


  Any better suggestions or at least where to seek ?

  


• FFMPEG codec "Error opening filters" error on Windows server

  12 février 2019, par Frank Nicklin

  Im using NReco Videoconvertor on and asp.net web service but its failing with the error

  ****Error : Cannot convert media : Error opening filters !****

  When testing on my local development PC Windows 10 VS2017 it works fine. If I manually run ffmpeg as this too work fine

  ffmpeg -i c:\tempfolder\5239.hevc c:\tempfolder\5239.mp4. 

  However if I try the same from my Windows 2016 Server I get a could not find codec parameters error :-

    D:\webservice\Bin>ffmpeg -i d:\video\1234.hevc d:\video\5225.mp4
  
  ffmpeg version N-56060-gbcd1c20 Copyright (c) 2000-2013 the FFmpeg developers
  
    built on Sep  6 2013 00:42:37 with gcc 4.7.3 (GCC)
  
    configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libcaca --enable-libfreetype --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxavs --enable-libxvid --enable-zlib
  
    libavutil      52. 43.100 / 52. 43.100
  
    libavcodec     55. 31.101 / 55. 31.101
  
    libavformat    55. 16.101 / 55. 16.101
  
    libavdevice    55.  3.100 / 55.  3.100
  
    libavfilter     3. 83.104 /  3. 83.104
  
    libswscale      2.  5.100 /  2.  5.100
  
    libswresample   0. 17.103 /  0. 17.103
  
    libpostproc    52.  3.100 / 52.  3.100
  
  [mov,mp4,m4a,3gp,3g2,mj2 @ 028fa380] Could not find codec parameters for stream 0 (Video: none (hvc1 / 0x31637668), 352x288, 937 kb/s): unknown codec
  
  Consider increasing the value for the 'analyzeduration' and 'probesize' options
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'd:\video\1234.hevc':
  
    Metadata:
  
      major_brand     : qt
  
      minor_version   : 0
  
      compatible_brands: qt
  
      creation_time   : 2019-02-04 10:35:12
  
    Duration: 00:00:20.25, start: 0.000000, bitrate: 965 kb/s
  
      Stream #0:0(und): Video: none (hvc1 / 0x31637668), 352x288, 937 kb/s, 30.01 fps, 30 tbr, 600 tbn, 600 tbc (default)
  
      Metadata:
  
        rotate          : 90
  
        creation_time   : 2019-02-04 10:35:12
  
        handler_name    : Core Media Video
  
      Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 22050 Hz, mono, fltp, 23 kb/s (default)
  
      Metadata:
  
        creation_time   : 2019-02-04 10:35:12
  
        handler_name    : Core Media Audio

  Any thoughts please.