[FFmpeg-devel] [PATCH] GSM 6.10 audio decoder

[Eli Friedman]

On Sat, Jul 3, 2010 at 4:51 PM, Eli Friedman <eli.friedman at gmail.com> wrote:
> On Sat, Jul 3, 2010 at 4:03 PM, Reimar D?ffinger
> <Reimar.Doeffinger at gmx.de> wrote:
>> Hello,
>> I fear I may have gone a bit too far when removing clipping protections,
>> however the clips I have (well, the three in samples/) decode bit-exact
>> compared to the libgsm decoder, and thanks to not trying to optimize for
>> 16-bit CPUs etc. it is a lot smaller and probably also faster (though
>> I did not care to benchmark).
>> When reviewing keep in mind that I think I've never implemented an
>> audio codec before :-)
>> As for the purpose: I want to throw out MPlayer's "native" variant
>> of this, which is basically libgsm just with a bit more of those horrible
>> old-style function declarations.
>
> I'd suggest writing out the formula for dequant_tab
> ("((idxb<<3)-28)*(idxa+1)", if I'm not mistaken) and getting rid of
> the table; unless I've really messed up the formula, it's cheap enough
> to compute on any processor with a decent multiplier that the table
> isn't worthwhile (e.g. it's two instructions on x86).

Wait, nevermind, for some reason I thought it was linear.

-Eli