[FFmpeg-devel] [PATCH] [3/3] SIPR 16k decoder

[Vitor Sessak]

Ronald S. Bultje wrote:
> Hi,
> 
> On Thu, Jan 14, 2010 at 7:30 PM, Ronald S. Bultje <rsbultje at gmail.com> wrote:
>> On Thu, Jan 14, 2010 at 7:25 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
>>> On Thu, Jan 14, 2010 at 07:19:47PM -0500, Ronald S. Bultje wrote:
>>>> On Thu, Jan 14, 2010 at 7:05 PM, Vitor Sessak <vitor1001 at gmail.com> wrote:
>>>>> The rule I use is: always use floats, unless when you need to call
>>>>> ff_acelp_lspd2lpc(), which takes doubles as arguments (and also to
>>>>> avoiding converting buffers to double or back).
>>>> So let's change ff_acelp_lspd2lpc()? Why does it use doubles?
>>> dont forget testing PSNR & with yor ears if PSNR differs
>>>
>>> i remember this double vs float discussion and the last time the awnser IIRC
>>> was that floats are not accurate enough. I dont want to see the floats are
>>> faster on my system so change it discussion repeat until testing is forgotten
>>> and we put a possibly hard to debug bug in
>> My point is more or less that *ALL* voice decoders should use doubles
>> everywhere.
> 
> Let me rephrase this before I say more stupid things that I didn't
> intend: if LSPs are double, then LSFs should be double also, and so
> should the code generating them.
> 
> Secondly, if LSPs are double, why are LPCs not double?

In the case of SIPR the reason has nothing to do with precision (the 
binary decoder is float-only). It is just for the sake of not creating 
yet another version of ff_acelp_lspd2lpc(), this time using floats.

-Vitor