[pulseaudio-discuss] [PATCH 3/6 v3] core: Add stereo to mono special case remapping

[Arun Raghavan]

On Tue, 2012-07-24 at 10:20 +0200, Peter Meerwald wrote:
> From: Peter Meerwald <p.meerwald at bct-electronic.com>
> 
> add special-case C code for stereo-to-mone remapping
[...] 
> +static void remap_stereo_to_mono_c(pa_remap_t *m, void *dst, const void *src, unsigned n) {
> +    unsigned i;
> +
> +    switch (*m->format) {
> +        case PA_SAMPLE_FLOAT32NE:
> +        {
> +            float *d = (float *) dst, *s = (float *) src;
> +
> +            for (i = n >> 2; i > 0; i--) {
> +                d[0] = s[0] + s[1];
> +                d[1] = s[2] + s[3];
> +                d[2] = s[4] + s[5];
> +                d[3] = s[6] + s[7];
> +                s += 8;
> +                d += 4;
> +            }
> +            for (i = n & 3; i; i--) {

Shouldn't this (and the next case) be (n & 2)?

> +                d[0] = s[0] + s[1];
> +                s += 2;
> +                d += 1;
> +            }
> +            break;
> +        }
> +        case PA_SAMPLE_S16NE:
> +        {
> +            int16_t *d = (int16_t *) dst, *s = (int16_t *) src;
> +
> +            for (i = n >> 2; i > 0; i--) {
> +                *d++ += s[0] + s[1];
> +                *d++ += s[2] + s[3];
> +                *d++ += s[4] + s[5];
> +                *d++ += s[6] + s[7];
> +                s += 8;
> +            }

Out of curiosity, is there a reason that you index d in the first case
and increment it in the second?

> +            for (i = n & 3; i; i--) {
> +                *d++ += s[0] + s[1];
> +                s += 2;
> +            }
> +            break;
> +        }
> +        default:
> +            pa_assert_not_reached();
> +    }
> +}

Regards,
Arun