[FFmpeg-devel] [PATCH] swresample/swresample: do not use s32p internally by default when resampling

wm4 nfxjfg at googlemail.com
Thu Mar 16 20:14:54 EET 2017


On Thu, 16 Mar 2017 17:00:17 +0700
Muhammad Faiz <mfcc64 at gmail.com> wrote:

> On Thu, Mar 16, 2017 at 1:01 PM, wm4 <nfxjfg at googlemail.com> wrote:
> > On Thu, 16 Mar 2017 12:43:10 +0700
> > Muhammad Faiz <mfcc64 at gmail.com> wrote:
> >  
> >> use fltp when doing s32 -> s32 resampling
> >> because s32p has no simd optimization
> >>
> >> benchmark:
> >> old 17.913s
> >> new  7.584s (use fma3)
> >>
> >> Signed-off-by: Muhammad Faiz <mfcc64 at gmail.com>
> >> ---
> >>  libswresample/swresample.c | 2 ++
> >>  1 file changed, 2 insertions(+)
> >>
> >> diff --git a/libswresample/swresample.c b/libswresample/swresample.c
> >> index f2e6600..74c96dc 100644
> >> --- a/libswresample/swresample.c
> >> +++ b/libswresample/swresample.c
> >> @@ -223,6 +223,8 @@ av_cold int swr_init(struct SwrContext *s){
> >>          }else if(   av_get_planar_sample_fmt(s-> in_sample_fmt) == AV_SAMPLE_FMT_S32P
> >>                   && av_get_planar_sample_fmt(s->out_sample_fmt) == AV_SAMPLE_FMT_S32P
> >>                   && !s->rematrix
> >> +                 && s->out_sample_rate == s->in_sample_rate
> >> +                 && !(s->flags & SWR_FLAG_RESAMPLE)
> >>                   && s->engine != SWR_ENGINE_SOXR){
> >>              s->int_sample_fmt= AV_SAMPLE_FMT_S32P;
> >>          }else if(av_get_bytes_per_sample(s->in_sample_fmt) <= 4){  
> >
> > Wouldn't going over float lose bits?  
> 
> Yes, of course. But when resampling with default opt, aliasing happens at
> about -90dB which is only 15 bits. Keeping 32 bits has no point at all.
> 
> > I guess most times, s32 is
> > actually 24 bit padded (since we have no 24 bit format). But it could
> > be true 32 bit as well (with all bits used). Or does it use double, or
> > am I missing something else?  
> 
> Using double is overkill, i think.

From my naive point of view this seems ok, then.


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