Clément Bœsch e4a27e2f2d lavc/arm: fix lack of precision in ff_ps_stereo_interpolate_neon
The code originally pre-multiply by 2 the steps, causing the running sum
of the h factors to drift away due to the lack of precision. It quickly
causes an inaccuracy > 0.01.

I tried diverse approaches such as multiply by 2.0 (instead of adding
the value itself) without success.

I'm unable to bench the impact of this change, feel free to compare.

This commit fixes the incoming aacpsdsp tests.

Following is an alternative simplified function (matching the incoming
AArch64 code) that may be used:

function ff_ps_stereo_interpolate_neon, export=1
        vld1.32         {q0}, [r2]
        vld1.32         {q1}, [r3]
        ldr             r12, [sp]
        vmov.f32        q8, q0
        vmov.f32        q9, q1
        vzip.32         q8, q0
        vzip.32         q9, q1
1:
        vld1.32         {d4}, [r0,:64]
        vld1.32         {d6}, [r1,:64]
        vadd.f32        q8, q8, q9
        vadd.f32        q0, q0, q1
        vmov.f32        d5, d4
        vmov.f32        d7, d6
        vmul.f32        q2, q2, q8
        vmla.f32        q2, q3, q0
        vst1.32         {d4}, [r0,:64]!
        vst1.32         {d5}, [r1,:64]!
        subs            r12, r12, 
        bgt             1b
        bx              lr
endfunc
2017-06-28 11:59:34 +02:00
2017-06-27 20:45:55 -03:00

FFmpeg README

FFmpeg is a collection of libraries and tools to process multimedia content such as audio, video, subtitles and related metadata.

Libraries

  • libavcodec provides implementation of a wider range of codecs.
  • libavformat implements streaming protocols, container formats and basic I/O access.
  • libavutil includes hashers, decompressors and miscellaneous utility functions.
  • libavfilter provides a mean to alter decoded Audio and Video through chain of filters.
  • libavdevice provides an abstraction to access capture and playback devices.
  • libswresample implements audio mixing and resampling routines.
  • libswscale implements color conversion and scaling routines.

Tools

  • ffmpeg is a command line toolbox to manipulate, convert and stream multimedia content.
  • ffplay is a minimalistic multimedia player.
  • ffprobe is a simple analysis tool to inspect multimedia content.
  • ffserver is a multimedia streaming server for live broadcasts.
  • Additional small tools such as aviocat, ismindex and qt-faststart.

Documentation

The offline documentation is available in the doc/ directory.

The online documentation is available in the main website and in the wiki.

Examples

Coding examples are available in the doc/examples directory.

License

FFmpeg codebase is mainly LGPL-licensed with optional components licensed under GPL. Please refer to the LICENSE file for detailed information.

Contributing

Patches should be submitted to the ffmpeg-devel mailing list using git format-patch or git send-email. Github pull requests should be avoided because they are not part of our review process and will be ignored.

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