[FFmpeg-devel] [RFC] ac3dec: use dsputil.clear_block
Thu Jan 14 02:54:37 CET 2010
Michael Niedermayer wrote:
> On Wed, Jan 13, 2010 at 06:32:27PM -0500, Justin Ruggles wrote:
>> 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:
>>>>> 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
>>> 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.
> are the float coeffs ever written to besides in int32_to_float_fmul_scalar ?
> because if not you could keep track of the last non zero coeff and just
> zero upto that each time
The bandwidth can change from block to block, so there could be leftover
higher frequency coeffs from the last block.
More information about the ffmpeg-devel