[FFmpeg-devel] [PATCH] Implement AAC Long Term Prediction (LTP) decoding module

Young Han Lee cpumaker
Fri Feb 11 02:46:58 CET 2011

On Thu, Feb 10, 2011 at 6:05 PM, Rob <robert.swain at gmail.com> wrote:

> On 10 February 2011 09:46, Rob <robert.swain at gmail.com> wrote:
> > On 10 February 2011 06:23, Alex Converse <alex.converse at gmail.com>
> wrote:
> >> This version looks good.
> >>
> >> Does anyone else have comments?
> >
> > I'll have a look over it shortly.
> My only concerns are that the expansion/addition of data arrays is
> significant. There's a 1024 element float array, a 3072 element
> int16_t array and an additional 1024 elements in another float array.
> I'm not saying that this needs to block merging, but if there is a way
> to improve it, perhaps we can add some comments as to how.
one of 1024 element float array (saved_ltp) is merged.
I'm thinking about how to merge the rest of additional data arrays
but I don't have good idea right now.

And the "ret" data array is reduced to 1024.
I think it could be missed when the imdct_half was implemented.
please check this out.

Is the int16_t array really needed? We output float anyway don't we so
> perhaps there is a way to translate the method to use float all the
> way through. I seem to remember when I switched to using imdct_half
> and vector_fmul I was able to reduce the array sizes somewhat. Is
> there any possibility of this for this ltp code? Things like that.
In the MPEG document, "short" type was recommended but,
it is not a big problem to change the type to float.
However, the array size will be double.
Do I change to float or not?

I'll consider about the possibility of method you used.
but it needs time :).

Generally, the code looks very neat and gets the OK from me as long as
> it has been tested with relevant clips and works. :) Good job!
> Regards,
> Rob
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Young Han
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