[FFmpeg-devel] [PATCH 3/3] Allow either float or int16_t input and output in ff_iir_filter().

[Måns Rullgård]

Justin Ruggles <justin.ruggles at gmail.com> writes:

> ---
>  libavcodec/iirfilter.c |  103 +++++++++++++++++++++++++++++++----------------
>  libavcodec/iirfilter.h |    3 +-
>  libavcodec/psymodel.c  |    3 +-
>  3 files changed, 72 insertions(+), 37 deletions(-)
>
>
>  void ff_iir_filter(const struct FFIIRFilterCoeffs *c, struct FFIIRFilterState *s,
> -                   int size, const int16_t *src, int sstep, int16_t *dst, int dstep)
> +                   int size, const void *src, int sstep, void *dst, int dstep,
> +                   enum AVSampleFormat sample_fmt)
>  {
> -    int i;
> -
> -    if(c->order == 4){
> -        for(i = 0; i < size; i += 4){
> -            float in, res;
> -
> -            FILTER(0, 1, 2, 3);
> -            FILTER(1, 2, 3, 0);
> -            FILTER(2, 3, 0, 1);
> -            FILTER(3, 0, 1, 2);
> -        }
> -    }else{
> -        for(i = 0; i < size; i++){
> -            int j;
> -            float in, res;
> -            in = *src * c->gain;
> -            for(j = 0; j < c->order; j++)
> -                in += c->cy[j] * s->x[j];
> -            res = s->x[0] + in + s->x[c->order >> 1] * c->cx[c->order >> 1];
> -            for(j = 1; j < c->order >> 1; j++)
> -                res += (s->x[j] + s->x[c->order - j]) * c->cx[j];
> -            for(j = 0; j < c->order - 1; j++)
> -                s->x[j] = s->x[j + 1];
> -            *dst = av_clip_int16(lrintf(res));
> -            s->x[c->order - 1] = in;
> -            src += sstep;
> -            dst += dstep;
> -        }
> +    if (!(sample_fmt == AV_SAMPLE_FMT_S16 || sample_fmt == AV_SAMPLE_FMT_FLT))
> +        return;
> +
> +    if (sample_fmt == AV_SAMPLE_FMT_S16) {
> +        void (*conv_filter_output)(float, void *) = conv_filter_output_s16;
> +        if (c->order == 4)
> +            FILTER4(int16_t)
> +        else
> +            FILTER_DIRECT_FORM_II(int16_t)
> +    } else {
> +        void (*conv_filter_output)(float, void *) = conv_filter_output_flt;
> +        if (c->order == 4)
> +            FILTER4(float)
> +        else
> +            FILTER_DIRECT_FORM_II(float)

I think two different functions would be preferable.  Fewer branches
(and parameters) is always better, and I dread to think what some
compilers might do with code like the above.  Also consider that we
might want to write asm versions of those some day.  That is much
easier if they are separated.

-- 
M?ns Rullg?rd
mans at mansr.com