[Ffmpeg-devel] mpegaudiodec.c and armv5te optimizations

Michael Niedermayer michaelni
Tue Oct 3 22:34:21 CEST 2006


On Tue, Oct 03, 2006 at 10:11:59PM +0300, Siarhei Siamashka wrote:
> Hello All,
> I would like to ask those who are familiar with mp3 decoding algorithm
> in mpegaudiodec.c better if there could be any really nasty things
> happening after changing current
> #define MULH(a,b) (((int64_t)(a) * (int64_t)(b))>>32)
> #define FIXHR(a) ((int)((a) * (1LL<<32) + 0.5))
> to something like
> #define MULH(a,b) (((int64_t)(a) * (int16_t)(b))>>16)
> #define FIXHR(a) ((int16_t)((a) * (1LL<<16) + 0.5))
> in low quality decoding mode.
> I tried to decode a few mp3 files and the difference does not seem to be very
> noticeable (samples seem to differ +-4 at most).

i think the change should be ok (for ARM) for x86 it should be slower

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

In the past you could go to a library and read, borrow or copy any book
Today you'd get arrested for mere telling someone where the library is

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