[FFmpeg-devel] [RFC] ac3dec: use dsputil.clear_block

Justin Ruggles justin.ruggles
Thu Jan 14 00:32:27 CET 2010

Reimar D?ffinger wrote:

> On Wed, Jan 13, 2010 at 11:42:27PM +0100, Michael Niedermayer wrote:
>> On Wed, Jan 13, 2010 at 09:46:17PM +0100, Reimar D?ffinger wrote:
>>> Hello,
>>> this gives an overall speedup of about 1.1 % on Intel Atom with my sample.
>>> Testing with other CPUs and samples heavily welcome, I suspect a slowdown may 
>>> be possible, beside it being a bit ugly.
>> what happens with these coeffs afterwards?
>> is it
>> s->dsp.int32_to_float_fmul_scalar(s->transform_coeffs[ch], s->fixed_coeffs[ch], gain, 256);
>> ?
>> if so maybe that could be changed to not touch the supposed to be zero
>> coeffs?
> I had that idea as well, but I have to admit I do not know, nor if I will have the time
> to understand the code well enough to know :-)

Yes the only time they're used is when they're converted to float.  If
we don't zero the integer coeffs, we will need to zero the float coeffs
because the IMDCT uses all 256.

But maybe we can zero them just prior to the IMDCT so that it will
benefit from the reduced number of channels because of pre-IMDCT downmixing.


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