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• lavc/qsv_hevc : correct QSV HEVC default plugin on Windows

  12 décembre 2018, par Zhong Li

  lavc/qsv_hevc : correct QSV HEVC default plugin on Windows
  1. Old logic meaned : everywhere, except Windows, ffmpeg has to use HW
  
  acceleration, but on Windows ffmpeg has to use (unavailable) software
  
  HEVC by default
  
  2. Software HEVC is available only if you provide corresponding
  
  software MediaSDK library, which isn't provided with ffmpeg. More
  
  information could be found in
  
  https://github.com/Intel-Media-SDK/MediaSDK/blob/master/doc/samples/readme-encode_linux.pdf
  
  3. HW HEVC decoding/encoding are available on Windows in the driver by default
  Note : Default case should be the most common case but this change still has potential risk
  
  on windows if HW path is not supported(or doesn't work as expection).
  
  (See the historical disscution : https://lists.libav.org/pipermail/libav-devel/2016-November/080419.html).
  
  In such case, two options suggested :
  
  1. Use the option "-load_plugin hevc_sw" to switch SW path manually.
  
  2. Or report bug to Intel windows driver if your GPU can support HEVC HW codec.
  
    (HEVC decoding is supported since Braswell, and encoding supported since Skylake)
  Patch started by Landgraph. Add similar change for hevc decoder and bump a new version.
  Reviewed-by : Mark Thompson <sw@jkqxz.net>
  
  Reviewed-by : Maxym Dmytrychenko <maxim.d33@gmail.com>
  
  Signed-off-by : Landgraph <me@landgraph.ru>
  
  Signed-off-by : Zhong Li <zhong.li@intel.com>
  

  • [DH] libavcodec/qsvdec_h2645.c
  • [DH] libavcodec/qsvenc_hevc.c
  • [DH] libavcodec/version.h

• 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

• avconv (ffmpeg) : correct audio codec

  1er juin 2015, par DmitryR

  I have an error when tryying to convert video from flash recorder to mp4 :

  ubuntu@media:/data/media/failed$ avconv -i videoStream_1356794393712_805.flv -acodec aac  videoStream_1356794393712_805.mp4
  
  avconv version 0.8.4-4:0.8.4-0ubuntu0.12.04.1, Copyright (c) 2000-2012 the Libav developers
  
    built on Nov  6 2012 16:51:33 with gcc 4.6.3
  
  [libspeex @ 0x1091500] Missing Speex header, assuming defaults.
  
  [flv @ 0x108d7a0] Estimating duration from bitrate, this may be inaccurate
  
  Input #0, flv, from 'videoStream_1356794393712_805.flv':
  
    Metadata:
  
      creationdate    : Sat Dec 29 15:20:12
  
    Duration: 00:00:04.39, start: 0.000000, bitrate: N/A
  
      Stream #0.0: Video: h264 (Main), yuv420p, 640x480 [PAR 1:1 DAR 4:3], 30 tbr, 1k tbn, 60 tbc
  
      Stream #0.1: Audio: libspeex, 16000 Hz, 1 channels, s16
  
  [buffer @ 0x1093a00] w:640 h:480 pixfmt:yuv420p
  
  [mpeg4 @ 0x1094ce0] removing common factors from framerate
  
  [aac @ 0x108d120] Too many bits per frame requested
  
  Output #0, mp4, to 'videoStream_1356794393712_805.mp4':
  
    Metadata:
  
      creationdate    : Sat Dec 29 15:20:12
  
      Stream #0.0: Video: mpeg4, yuv420p, 640x480 [PAR 1:1 DAR 4:3], q=2-31, 200 kb/s, 90k tbn, 30 tbc
  
      Stream #0.1: Audio: aac, 16000 Hz, 1 channels, s16, 200 kb/s
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (h264 -> mpeg4)
  
    Stream #0:1 -> #0:1 (libspeex -> aac)
  
  Error while opening encoder for output stream #0:1 - maybe incorrect parameters such as bit_rate, rate, width or height
  
  ubuntu@media:/data/media/failed$

  Ubuntu 12.04 LTS, default ffmpeg/avconv.
  How can I solve this problem ?

  ffprobe log :

  ubuntu@media:/data/media/failed$ ffprobe videoStream_1356794393712_805.flv
  
  avprobe version 0.8.4-4:0.8.4-0ubuntu0.12.04.1, Copyright (c) 2007-2012 the Libav developers
  
    built on Nov  6 2012 16:51:33 with gcc 4.6.3
  
  [libspeex @ 0x1c27500] Missing Speex header, assuming defaults.
  
  [flv @ 0x1c237a0] Estimating duration from bitrate, this may be inaccurate
  
  Input #0, flv, from 'videoStream_1356794393712_805.flv':
  
    Metadata:
  
      creationdate    : Sat Dec 29 15:20:12
  
    Duration: 00:00:04.39, start: 0.000000, bitrate: N/A
  
      Stream #0.0: Video: h264 (Main), yuv420p, 640x480 [PAR 1:1 DAR 4:3], 30 tbr, 1k tbn, 60 tbc
  
      Stream #0.1: Audio: libspeex, 16000 Hz, 1 channels, s16
  
  [libspeex @ 0x1c27500] Missing Speex header, assuming defaults.
  
  ubuntu@media:/data/media/failed$