Re: [Bluez-devel] sbc and fixed-point progress

Brad Midgley
2005-09-03T16:05:09Z

Victor

Excellent... I applied the patches.

Brad

Victor Shcherbatyuk wrote:
> Brad,
>
> The patch includes restructured and cleaned up code for 8-subband fixed
> point encoder (I didn't touch a2play yet). I've removed some of your
> code (if you need it let me know), moved fixed tables to sbc_tables.h
> (manually), merged floating and fixed point filter code. Now all the
> math is in sbc_math.h, an option added for 32 bit fixed point, but I
> could not make it sound any good, it is uses ~0% cpu producing sound of
> 0 quality - looks fair, so if someone wants to experiment with it... :)
>
> I will do 4 subband encoder too. Can not promise any dates, depends how
> easy it goes...
>
> I've played with Philips codec and I've noticed one thing. With the same
> value of bitpool our codec produces bitrate half of what the Philips
> codec does... So, if I set bitpool 15 for the Philips codec it will
> produce the same bitrate and sound quality as our encoder produces with
> bitpool eq. 32 - something might be wrong with bitallocation?
>
> Regards,
> Victor.
>
> P.S. There is no real need in rmagnitude() as we can test the filter
> code for overflowing using an test app, supplying all kind of inputs and
> comparing its output with that of the floating point filer. I've done it
> and currently it does not overflow, later if we need more precision? we
> can tweak SCALE_STAGE1 and SCALE_STAGE2 to get maximum of precision
> without overflowing....