[pulseaudio-discuss] [PATCH] Optimize trivial resampler

[Maarten Bosmans]

Hmm, I don't think frames are garantueed to be aligned, only samples
are. So this patch probably needs some tweaking.

Maarten

2011/10/12 Maarten Bosmans <mkbosmans at gmail.com>:
> Together with the disabling of the assert in the loop, this improves
> the performance of s16 2ch resampling by 4.5x.
> ---
>  src/pulsecore/resampler.c |   21 +++++++++++++--------
>  1 files changed, 13 insertions(+), 8 deletions(-)
>
> diff --git a/src/pulsecore/resampler.c b/src/pulsecore/resampler.c
> index c3b6df1..3ca0a2f 100644
> --- a/src/pulsecore/resampler.c
> +++ b/src/pulsecore/resampler.c
> @@ -1369,7 +1369,7 @@ static int speex_init(pa_resampler *r) {
>
>  static void trivial_resample(pa_resampler *r, const pa_memchunk *input, unsigned in_n_frames, pa_memchunk *output, unsigned *out_n_frames) {
>     size_t fz;
> -    unsigned o_index;
> +    unsigned i_index, o_index;
>     void *src, *dst;
>
>     pa_assert(r);
> @@ -1383,18 +1383,23 @@ static void trivial_resample(pa_resampler *r, const pa_memchunk *input, unsigned
>     dst = (uint8_t*) pa_memblock_acquire(output->memblock) + output->index;
>
>     for (o_index = 0;; o_index++, r->trivial.o_counter++) {
> -        unsigned j;
> +        i_index = ((r->trivial.o_counter * r->i_ss.rate) / r->o_ss.rate);
> +        i_index = i_index > r->trivial.i_counter ? i_index - r->trivial.i_counter : 0;
>
> -        j = ((r->trivial.o_counter * r->i_ss.rate) / r->o_ss.rate);
> -        j = j > r->trivial.i_counter ? j - r->trivial.i_counter : 0;
> -
> -        if (j >= in_n_frames)
> +        if (i_index >= in_n_frames)
>             break;
>
>         pa_assert_fp(o_index * fz < pa_memblock_get_length(output->memblock));
>
> -        memcpy((uint8_t*) dst + fz * o_index,
> -                   (uint8_t*) src + fz * j, (int) fz);
> +        /* Directly assign some common sizes, use memcpy as fallback */
> +        if (fz == 2)
> +          ((uint16_t *) dst)[o_index] = ((uint16_t *) src)[i_index];
> +        else if (fz == 4)
> +          ((uint32_t *) dst)[o_index] = ((uint32_t *) src)[i_index];
> +        else if (fz == 8)
> +          ((uint64_t *) dst)[o_index] = ((uint64_t *) src)[i_index];
> +        else
> +            memcpy((uint8_t *) dst + fz * o_index, (uint8_t *) src + fz * i_index, (int) fz);
>     }
>
>     pa_memblock_release(input->memblock);
> --
> 1.7.4.1
>
>