[CELT-dev] fixed point code

Jean-Marc Valin jmvalin at jmvalin.ca
Thu Mar 3 13:25:44 PST 2011


"J.B. (Jae) Hong" <jbhong at broadcom.com> a écrit :
> Could you provide us with fixed-point code for initialization of  
> this array? Or you may kindly provide us with ROM tables of the  
> array for each possible combination of frame size and sampling  
> freq...?

ROM tables are already included for frame sizes 120,240,480,960 at 48  
kHz. For the others, you can use the dump_modes utility with the  
sampling rate(s) and frame size(s) you need.

> [2] Usage on global stack memory
> In "arch.h", there is a definition on the following constant for  
> global processing memory (stack RAM).
> #define GLOBAL_STACK_SIZE 100000

This "global stack" is only a fall-back when neither C99  
variable-length arrays, nor alloca() are available. See if you can use  
one of those instead. For that, all you need is define either  

> -          Peak state memory (static RAM) size?
> -          Peak processing RAM size including local stack RAM  
> (100,000 bytes?)?

I have not measured those, but I'm sure it's under 100k. Also, it's  
probably possible to make CELT more efficient than it currently is  
when it comes to stack size.

> -          Minimum input bit-stream buffer size with maximum  
> bit-rate per frame considered at 48KHz sampling rate?

If by that you mean the largest compressed packet that can exist, then  
the answer is 1275 bytes.


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