# [Freeswitch-dev] Codes I don't understand

seven du seven at idapted.com
Mon Apr 6 08:44:06 PDT 2009

```Well, Thank you Anthony. 3 questions In summary,

1) in
>                        if (x < rlen) {
>                                z += (int32_t) *(fp + x);

Any difference if change the "+=" to "=" since z is 0? It just
confused me.

2)  If n1 = 32768, n2 = 32766,  after use MACRO
switch_normalize_to_16bit(n1)
switch_normalize_to_16bit(n2)

the result will be:
n1 = 32767/2 = 16383
n2 = 32766

is that the expected result?

3) Is there any chance rlen and wlen both > 0?

On Apr 6, 2009, at 11:16 PM, Anthony Minessale wrote:

> what ?
>
> I don't know what your question is.
>
>
> On Mon, Apr 6, 2009 at 9:35 AM, seven du <seven at idapted.com> wrote:
> Hi, can someone explain this  to me?
>
> In switch_core_media_bug.c, around line 173:
>
>
>
>                for (x = 0; x < blen; x++) {
>                        int32_t z = 0;
>
>                        if (x < rlen) {
>                                z += (int32_t) *(fp + x);     //
> what's difference here with z =
> (int32_t) *(fp + x) ?
>
>                        }
>                        if (x < wlen) {
>                                z += (int32_t) *(dp + x);
>                        }
>                        switch_normalize_to_16bit(z);
>                        *(fp + x) = (int16_t) z / 2;
>                }
>
> And for switch_normalize_to_16bit, according to switch_utils.h,
>
> #define SWITCH_SMAX 32767
> #define SWITCH_SMIN -32768
> #define switch_normalize_to_16bit(n) if (n > SWITCH_SMAX) n =
> SWITCH_SMAX / 2; else if (n < SWITCH_SMIN) n = SWITCH_SMIN / 2;
>
> Then
> switch_normalize_to_16bit( 32768 ), z = 32767/2, and (int16_t) z / 2 =
> 32767/4
> switch_normalize_to_16bit( 32766) , z = 32766, and (int16_t) z / 2 =
> 32766/2
>
> Does that make sense? I guess it should be like this:
>
> #define switch_normalize_to_16bit(n) if (n > SWITCH_SMAX) n =
> SWITCH_SMAX / 2; else if (n < SWITCH_SMIN) n = SWITCH_SMIN / 2; else n
> = n / 2;
>
>                        switch_normalize_to_16bit(z);
>                        *(fp + x) = (int16_t) z;
>
>
> Thank you.
>
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>
> --
> Anthony Minessale II
>
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