[LAD] Regarding amplifying a PCM frame

[Peter Nelson]

On Mon, 2009-10-26 at 15:05 -0700, Drip Stone wrote:
> Hi,
> 
> Thank you for providing valuable information. I will put some code
> here:
> 
>     while ( 1 )
>     {
>         for ( int i = 0; i < frames; i++ )
>         {
>             float t = 0;
>             if ( left )    //for left channel
>             {
>                 t = *((float*)&(fbuffer[pos+i*4]));    //4 bytes each
> frame
>                 t*=2;
>                 //printf("%f ",t);
>                 for ( int j = 0; j < 4; j++ )
>                     buffer[i*8+j] = ((char*)&t)[j];    //8 bytes for 2
> channels
>             }
> 
>         rc = snd_pcm_writei ( handle, buffer, frames );
>         pos += frames * 4; 
>     }
> 
> I think the value is not out of [-1.0,1.0]. BTW, what does it mean
> when a value is negative?
> 
Ouch, you're doing a byte-by-byte copy of a 32bit float?? Please, just
use the correct data types.

Floating point audio data is usually signed, so -1.0 and 1.0 are the
farthest extents, and 0.0 would be the default no-signal state.

Peter.