opus - Dec 2014 - [RFC][FFT][Fixed-Point][NEON] NEON-Optimize

Hi Timothy,



It requires some extra effort if twiddles and input/output have different bit
width.  Since Opus uses int32 for twiddles, we are going to do the same thing.



Thanks,

Phil Wang

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On 28/12/14 11:04 PM, Phil Wang wrote:
> It requires some extra effort if twiddles and input/output have
> different bit width.  Since Opus uses int32 for twiddles, we are going
> to do the same thing.
Actually, the existing Opus code has 16-bit twiddles, mostly because it
makes it possible to use smulwb on ARMv5E. That being said, I agree that
for Neon it makes sense to use 32-bit twiddles since there's no 16x32
multiplier.

Cheers,

	Jean-Marc
>  
> 
> Thanks,
> 
> Phil Wang
> 
> 
> -- IMPORTANT NOTICE: The contents of this email and any attachments are
> confidential and may also be privileged. If you are not the intended
> recipient, please notify the sender immediately and do not disclose the
> contents to any other person, use it for any purpose, or store or copy
> the information in any medium. Thank you.
> 
> ARM Limited, Registered office 110 Fulbourn Road, Cambridge CB1 9NJ,
> Registered in England & Wales, Company No: 2557590
> ARM Holdings plc, Registered office 110 Fulbourn Road, Cambridge CB1
> 9NJ, Registered in England & Wales, Company No: 2548782
> 
> 
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Hi Jean-Marc,

I have implemented fixed-point FFT with 32-bit twiddles. Now I want to
evaluate the accuracy, what method does Opus use?
I use function implemented inside Ne10 to calculate SNR. Any comment?

|  size |    SNR (dB)  |
|   16  | 82.558587 |
|   32  | 83.530298 |
|   60  | 80.292433 |
|   64  | 82.752950 |
| 120  | 79.625077 |
| 128  | 83.091260 |
| 240  | 79.555263 |
| 256  | 82.470671 |
| 480  | 79.741435 |
| 512  | 82.675800 |
| 900  | 79.098034 |
| 960  | 79.737709 |

If Opus are using other method to evaluate the accuracy, can you kindly show
me the path?

Best Regards,
Phil Wang
> -----Original Message-----
> From: Jean-Marc Valin [mailto:jmvalin at jmvalin.ca]
> Sent: Tuesday, December 30, 2014 3:30 AM
> To: Phil Wang; opus at xiph.org; Timothy B. Terriberry (tterribe at
xiph.org)
> Cc: Zhongwei Yao; Yang Zhang; Zhou (Joe) Yu; Steve Bannister
> Subject: Re: [opus] [Opus][RFC][FFT][Fixed-Point][NEON] NEON-Optimize
> 
> On 28/12/14 11:04 PM, Phil Wang wrote:
> > It requires some extra effort if twiddles and input/output have
> > different bit width.  Since Opus uses int32 for twiddles, we are going
> > to do the same thing.
> 
> Actually, the existing Opus code has 16-bit twiddles, mostly because it
makes
> it possible to use smulwb on ARMv5E. That being said, I agree that for
Neon it
> makes sense to use 32-bit twiddles since there's no 16x32 multiplier.
> 
> Cheers,
> 
> 	Jean-Marc
> 
> >
> >
> > Thanks,
> >
> > Phil Wang
> >
> >
> > -- IMPORTANT NOTICE: The contents of this email and any attachments
> > are confidential and may also be privileged. If you are not the
> > intended recipient, please notify the sender immediately and do not
> > disclose the contents to any other person, use it for any purpose, or
> > store or copy the information in any medium. Thank you.
> >
> > ARM Limited, Registered office 110 Fulbourn Road, Cambridge CB1 9NJ,
> > Registered in England & Wales, Company No: 2557590 ARM Holdings
plc,
> > Registered office 110 Fulbourn Road, Cambridge CB1 9NJ, Registered in
> > England & Wales, Company No: 2548782
> >
> >
> > _______________________________________________
> > opus mailing list
> > opus at xiph.org
> > http://lists.xiph.org/mailman/listinfo/opus
> >