[FFmpeg-devel] [PATCH] AMR-WB Decoder

[Måns Rullgård]

"Ronald S. Bultje" <rsbultje at gmail.com> writes:

> Hi,
>
> 2010/9/18 Marcelo Galv?o P?voa <marspeoplester at gmail.com>:
>> On 18 September 2010 22:27, Ronald S. Bultje <rsbultje at gmail.com> wrote:
>>> What "random" number generator does the ref decoder use? Is it an algo
>>> that you can copy, or is it literally "random()"?
>>
>> It is simple:
>>
>> Word16 D_UTIL_random(Word16 *seed)
>> {
>> ? /*static Word16 seed = 21845;*/
>> ? *seed = (Word16)(*seed * 31821L + 13849L);
>> ? return(*seed);
>> }
>
> So why don't we use that also

Using a better RNG probably gives better output, even if it deviates
from the reference.

> at least if s->flags & CODEC_FLAG_BITEXACT is set?

That's not what that flag is for.  The BITEXACT flag should only be
used to disable asm optimisations differing from our C code, e.g. some
of the IDCTs.

-- 
M?ns Rullg?rd
mans at mansr.com