Re[2]: III_requantize question

Hello Rob,

Monday, October 20, 2003, 7:04:18 PM, you wrote:
RL> On Sunday, October 19, 2003, at 10:47  PM, Grigory Abuladze wrote:
>> I am working with mad-0.15.0
>> I hope someone may give me answer on this questions:
>>
>> 1. The result of this function III_exponents() in layer3.c file is
>>    signed int exponents[39] array. My question - in which format
>>    is result presented?

RL> The resulting exponents represent multiples of 1/4 -- in other words, 
RL> imagine a fixed binary point to the left of the two least significant 
RL> bits.

>> 2.
>>       Xr = is^(4/3) * 2^(exp)       (sign not discussed)
>>
>>       What value exp can be and what step?
>>       -88.5 <= exp <= 11.5, 0 <= is[i] <= 8207
>>       are this equation true?

RL> I calculate -81.5 <= exp <= 11.25 based on the theoretical limits of 
RL> the requantization formula variables.

RL> Also 0 <= is[i] <= 8206, although there is some debate over whether 
RL> ISO/IEC 11172-3 actually permits values greater than 8191.

>>       From III_requantize() it is look like step is 2^(1/4) - where 
>> can I take this information?

RL> Yes, from the requantization and scaling formula presented in ISO/IEC 
RL> 11172-3, the exponent may be a multiple of 1/4 depending on global_gain 
RL> and, for short blocks, subblock_gain[w].

Thanks for answer!

and one more
Does it true    |Xr|<1     ?
and is[i] & exp managed so above statement is always correct?

Thanks.
-- 
Best regards,
 Grigory                            mailto:[email protected]