[FFmpeg-devel] [PATCH] atrac decoder

Måns Rullgård mans
Wed Aug 12 22:06:23 CEST 2009


Benjamin Larsson <banan at ludd.ltu.se> writes:

> Michael Niedermayer wrote:
>>>>
>>> Well as vector_fmul_window is defined now you need to use the complete
>>> windows.
>> 
>> and when window is 0 or 1 some other function could be used, besides
>> is vector_fmul_window + half_imdct slower than the cutrrent code?
>> 
>
> I did a test run that used one call to imdct_half and on call to
> vector_fmul_window per time the imdct function was invoked (ie it didn't
> decode properly it was just the same amount of calls). I got these numbers:
>
> mdct_regular
> 192195 dezicycles in mdct, 127 runs, 1 skips
> 190436 dezicycles in mdct, 255 runs, 1 skips
> 189578 dezicycles in mdct, 511 runs, 1 skips
> 190527 dezicycles in mdct, 1021 runs, 3 skips
> 190002 dezicycles in mdct, 2043 runs, 5 skips
> 188916 dezicycles in mdct, 4086 runs, 10 skips
> 188563 dezicycles in mdct, 8173 runs, 19 skips/s
>
> mdct_half
> 162004 dezicycles in mdct, 127 runs, 1 skips
> 161286 dezicycles in mdct, 255 runs, 1 skips
> 163959 dezicycles in mdct, 511 runs, 1 skips
> 164064 dezicycles in mdct, 1022 runs, 2 skips
> 163556 dezicycles in mdct, 2043 runs, 5 skips
> 163445 dezicycles in mdct, 4088 runs, 8 skipss/s
> 163775 dezicycles in mdct, 8180 runs, 12 skips/s
>
> Is that difference worth the extra memory needed for the mdct windows ?

That's a significant speedup.  How much memory are we talking about?

-- 
M?ns Rullg?rd
mans at mansr.com



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