Is 8-bit Audio Unsigned?

Chris Barrett wrote:
> I've found that I've been forced to use an if statement to read 24-bit
> audio.  I'm doing this with the following code:
>
>
> //-------------------------------------------------
> long data24;
>
> fread(&data24,sampleSize,1,file_In);
> if(data24 > 8388607)
> 	array1[i] =  (data24)/8388608.0 - 2.0;
> if(data24 <= 8388607)
> 	array1[i] =  (data24)/8388608.0;
> //-----------------------------------------------
>
>
> The strange thing is that I've been able to write it without using an if
> statement.  I've done this using the following code:
>
>
> //------------------------------------------------
> long signed data24;
>
> data24 = (long)floor((array2[i])*8388608.0+0.5);
> fwrite(&data24,sampleSize,1,file_out);
> //-----------------------------------------------
>
>
> This makes no sense to me.  How can it require an if statement to read,
> but not one to write? Is there a way around this?

You are using a long data type, which is 32-bits on many systems.
Your reader will work whether or not the upper 8 bits are all ones.
Your writer will always fill the upper 8 bits with ones (given full
range signals), which may not be symmetric and might fool some
readers which assume the upper 8 bits have some other meaning.
If you only write out the bottom 24 bits, then whether or not the
upper 8 bits are correct or not may be irrelevant.


IMHO. YMMV.
-- 
rhn A.T nicholson d.0.t C-o-M