opus - Jan 2011 - drawback when using very small frame sizes ?

I have learned from the docs that minimum frame size is 64 samples/ch. = 1.33 ms
@ 48kHz.
Is there any drawback using this or maybe 128 in terms of quality or increased
load (compared to 512 samples) ?

thanks a lot,
Marko.


our config:
 - version = 0.9.1
 - ARM9E, FIXED_POINT, DOUBLE_PRECISION
 - f<s> = 48kHz
 - rate = 128 kbit/s (stereo)
 - vbr_rate = 0
 - prediction = 2
 - complexity = 10

Hi,

The smaller the frame size, the higher the bit-rate required to get the 
same quality. For tiny frame sizes, this is even more noticeable. As for 
the compile flags, I think 0.9.1 still required the MIXED_PRECISION to 
be defined for fixed-point. This is no longer the case for 0.10 and later.

Cheers,

	Jean-Marc

On 11-01-17 02:48 PM, Marko wrote:
>
> I have learned from the docs that minimum frame size is 64 samples/ch. =
1.33 ms @ 48kHz.
> Is there any drawback using this or maybe 128 in terms of quality or
increased load (compared to 512 samples) ?
>
> thanks a lot,
> Marko.
>
>
> our config:
>   - version = 0.9.1
>   - ARM9E, FIXED_POINT, DOUBLE_PRECISION
>   - f<s>  = 48kHz
>   - rate = 128 kbit/s (stereo)
>   - vbr_rate = 0
>   - prediction = 2
>   - complexity = 10
>
>
> _______________________________________________
> celt-dev mailing list
> celt-dev at xiph.org
> http://lists.xiph.org/mailman/listinfo/celt-dev
>
>

hi Jean-Marc,

thanks for your answer. 

1.
Can you give a rough estimation for the quality decrease, maybe in percentage of
required bit rate ?

2.
Is there a tool to meassure quality of a codec like CELT ?

regards,
Markus.

On Wed, Jan 19, 2011 at 1:41 PM, Marko <celt at platax.de>
wrote:
> hi Jean-Marc,
> thanks for your answer.
>
> 1.
> Can you give a rough estimation for the quality decrease, maybe in
percentage of required bit rate ?
>
> 2.
> Is there a tool to meassure quality of a codec like CELT ?
PEAQ.  E.g. PQEvalAudio in
http://www-mmsp.ece.mcgill.ca/documents/Downloads/AFsp/

There are PEAQ results on testing pages for some of our prior releases:
http://celt-codec.org/testing/test.0.6.0.shtml.en


However, it appears PEAQ understates the harm of smaller frame sizes
somewhat so take that with a healthy grain of salt.