1
0
mirror of https://github.com/FFmpeg/FFmpeg.git synced 2024-12-07 11:13:41 +02:00
FFmpeg/libavcodec/arm/fft_init_arm.c
Ben Avison 87552d54d3 armv6: Accelerate ff_fft_calc for general case (nbits != 4)
The previous implementation targeted DTS Coherent Acoustics, which only
requires nbits == 4 (fft16()). This case was (and still is) linked directly
rather than being indirected through ff_fft_calc_vfp(), but now the full
range from radix-4 up to radix-65536 is available. This benefits other codecs
such as AAC and AC3.

The implementaion is based upon the C version, with each routine larger than
radix-16 calling a hierarchy of smaller FFT functions, then performing a
post-processing pass. This pass benefits a lot from loop unrolling to
counter the long pipelines in the VFP. A relaxed calling standard also
reduces the overhead of the call hierarchy, and avoiding the excessive
inlining performed by GCC probably helps with I-cache utilisation too.

I benchmarked the result by measuring the number of gperftools samples that
hit anywhere in the AAC decoder (starting from aac_decode_frame()) or
specifically in the FFT routines (fft4() to fft512() and pass()) for the
same sample AAC stream:

              Before          After
              Mean   StdDev   Mean   StdDev  Confidence  Change
Audio decode  2245.5 53.1     1599.6 43.8    100.0%      +40.4%
FFT routines  940.6  22.0     348.1  20.8    100.0%      +170.2%

Signed-off-by: Martin Storsjö <martin@martin.st>
2014-07-18 01:34:23 +03:00

71 lines
2.2 KiB
C

/*
* Copyright (c) 2009 Mans Rullgard <mans@mansr.com>
*
* This file is part of Libav.
*
* Libav is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* Libav is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with Libav; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "libavutil/arm/cpu.h"
#include "libavcodec/fft.h"
#include "libavcodec/rdft.h"
#include "libavcodec/synth_filter.h"
void ff_fft_calc_vfp(FFTContext *s, FFTComplex *z);
void ff_fft_permute_neon(FFTContext *s, FFTComplex *z);
void ff_fft_calc_neon(FFTContext *s, FFTComplex *z);
void ff_imdct_half_vfp(FFTContext *s, FFTSample *output, const FFTSample *input);
void ff_imdct_calc_neon(FFTContext *s, FFTSample *output, const FFTSample *input);
void ff_imdct_half_neon(FFTContext *s, FFTSample *output, const FFTSample *input);
void ff_mdct_calc_neon(FFTContext *s, FFTSample *output, const FFTSample *input);
void ff_rdft_calc_neon(struct RDFTContext *s, FFTSample *z);
av_cold void ff_fft_init_arm(FFTContext *s)
{
int cpu_flags = av_get_cpu_flags();
if (have_vfp(cpu_flags) && !have_vfpv3(cpu_flags)) {
s->fft_calc = ff_fft_calc_vfp;
#if CONFIG_MDCT
s->imdct_half = ff_imdct_half_vfp;
#endif
}
if (have_neon(cpu_flags)) {
s->fft_permute = ff_fft_permute_neon;
s->fft_calc = ff_fft_calc_neon;
#if CONFIG_MDCT
s->imdct_calc = ff_imdct_calc_neon;
s->imdct_half = ff_imdct_half_neon;
s->mdct_calc = ff_mdct_calc_neon;
s->mdct_permutation = FF_MDCT_PERM_INTERLEAVE;
#endif
}
}
#if CONFIG_RDFT
av_cold void ff_rdft_init_arm(RDFTContext *s)
{
int cpu_flags = av_get_cpu_flags();
if (have_neon(cpu_flags))
s->rdft_calc = ff_rdft_calc_neon;
}
#endif