[FFmpeg-devel] [PATCH] atrac decoder

[Benjamin Larsson]

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 ?

MvH
Benjamin Larsson