[pulseaudio-discuss] [PATCH 1/4] Added libsoxr resampler backend.

[Peter Meerwald]

Hello Andrey,

> The new backend supports 4 quality levels: lq, mq, hq and vhq; 16 and 
> 32-bit integer samples and 32-bit float samples. The libsoxr resampler 
> generally offers better quality and speed compared to speex.

soxr support was proposed previously,
http://lists.freedesktop.org/archives/pulseaudio-discuss/2014-August/021050.html

the common consensus currently seems to be that soxr doesn't offer enough 
advantage to justify inclusion in PA

I think the claim "is almost always faster" needs to be substantiated; 
some comparison has been done here: http://poljar.blogspot.co.at/2013/08/vol-2-resampling-methods.html

I am  pro-choice wrt resamplers :)
on the other hand PA's framework to add more resamplers is not very 
sustainable (huge table with different qualities)

regards, p.

> ---
>  src/pulsecore/resampler/soxr.c | 168 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 168 insertions(+)
>  create mode 100644 src/pulsecore/resampler/soxr.c
> 
> diff --git a/src/pulsecore/resampler/soxr.c b/src/pulsecore/resampler/soxr.c
> new file mode 100644
> index 0000000..ba45d36
> --- /dev/null
> +++ b/src/pulsecore/resampler/soxr.c
> @@ -0,0 +1,168 @@
> +/***
> +  This file is part of PulseAudio.
> +
> +  Copyright 2014 Andrey Semashev
> +
> +  PulseAudio is free software; you can redistribute it and/or modify
> +  it under the terms of the GNU Lesser General Public License as published
> +  by the Free Software Foundation; either version 2.1 of the License,
> +  or (at your option) any later version.
> +
> +  PulseAudio is distributed in the hope that it will be useful, but
> +  WITHOUT ANY WARRANTY; without even the implied warranty of
> +  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> +  General Public License for more details.
> +
> +  You should have received a copy of the GNU Lesser General Public License
> +  along with PulseAudio; if not, write to the Free Software
> +  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
> +  USA.
> +***/
> +
> +#ifdef HAVE_CONFIG_H
> +#include <config.h>
> +#endif
> +
> +#include <stddef.h>
> +#include <soxr.h>
> +
> +#include <pulsecore/resampler.h>
> +
> +static unsigned resampler_soxr_resample(pa_resampler *r, const pa_memchunk *input, unsigned in_n_frames,
> +                                        pa_memchunk *output, unsigned *out_n_frames) {
> +    soxr_t state;
> +    void *in, *out;
> +    size_t consumed = 0, produced = 0;
> +
> +    pa_assert(r);
> +    pa_assert(input);
> +    pa_assert(output);
> +    pa_assert(out_n_frames);
> +
> +    state = r->impl.data;
> +    pa_assert(state);
> +
> +    in = pa_memblock_acquire_chunk(input);
> +    out = pa_memblock_acquire_chunk(output);
> +
> +    pa_assert_se(soxr_process(state, in, in_n_frames, &consumed, out, *out_n_frames, &produced) == 0);
> +
> +    pa_memblock_release(input->memblock);
> +    pa_memblock_release(output->memblock);
> +
> +    *out_n_frames = produced;
> +
> +    return in_n_frames - consumed;
> +}
> +
> +static void resampler_soxr_free(pa_resampler *r) {
> +    pa_assert(r);
> +
> +    if (!r->impl.data)
> +        return;
> +
> +    soxr_delete(r->impl.data);
> +    r->impl.data = NULL;
> +}
> +
> +static void resampler_soxr_reset(pa_resampler *r) {
> +    soxr_t old_state;
> +
> +    pa_assert(r);
> +
> +    /* This makes soxr_process() crash afterwards,
> +       so don't use this function until libsoxr is fixed.
> +    soxr_clear(r->impl.data); */
> +
> +    old_state = r->impl.data;
> +    r->impl.data = NULL;
> +
> +    if (pa_resampler_soxr_init(r) == 0) {
> +        if (old_state)
> +            soxr_delete(old_state);
> +    } else {
> +        r->impl.data = old_state;
> +        pa_log_error("Failed to reset libsoxr context");
> +    }
> +}
> +
> +static void resampler_soxr_update_rates(pa_resampler *r) {
> +    soxr_t old_state;
> +
> +    pa_assert(r);
> +
> +    /* There is no update method in libsoxr,
> +       so just re-create the resampler context */
> +
> +    old_state = r->impl.data;
> +    r->impl.data = NULL;
> +
> +    if (pa_resampler_soxr_init(r) == 0) {
> +        if (old_state)
> +            soxr_delete(old_state);
> +    } else {
> +        r->impl.data = old_state;
> +        pa_log_error("Failed to update libsoxr sample rates");
> +    }
> +}
> +
> +int pa_resampler_soxr_init(pa_resampler *r) {
> +    soxr_t state;
> +    soxr_datatype_t io_format;
> +    soxr_io_spec_t io_spec;
> +    unsigned long quality_recipe;
> +    soxr_quality_spec_t quality;
> +    soxr_error_t err = NULL;
> +
> +    pa_assert(r);
> +
> +    switch (r->work_format) {
> +        case PA_SAMPLE_S16NE:
> +            io_format = SOXR_INT16_I;
> +            break;
> +        case PA_SAMPLE_S32NE:
> +            io_format = SOXR_INT32_I;
> +            break;
> +        case PA_SAMPLE_FLOAT32NE:
> +            io_format = SOXR_FLOAT32_I;
> +            break;
> +        default:
> +            pa_assert(0 && "Unsupported sample format for libsoxr");
> +            return -1;
> +    }
> +
> +    io_spec = soxr_io_spec(io_format, io_format);
> +
> +    switch (r->method) {
> +        case PA_RESAMPLER_SOXR_LQ:
> +            quality_recipe = SOXR_LQ | SOXR_LINEAR_PHASE;
> +            break;
> +        case PA_RESAMPLER_SOXR_MQ:
> +            quality_recipe = SOXR_MQ | SOXR_LINEAR_PHASE;
> +            break;
> +        case PA_RESAMPLER_SOXR_VHQ:
> +            quality_recipe = SOXR_VHQ | SOXR_LINEAR_PHASE;
> +            break;
> +        default:
> +            pa_assert(0 && "Unexpected libsoxr resampling method");
> +        case PA_RESAMPLER_SOXR_HQ:
> +            quality_recipe = SOXR_HQ | SOXR_LINEAR_PHASE;
> +            break;
> +    }
> +
> +    quality = soxr_quality_spec(quality_recipe, 0);
> +
> +    state = soxr_create(r->i_ss.rate, r->o_ss.rate, r->work_channels, &err, &io_spec, &quality, NULL);
> +    if (!state) {
> +        pa_log_error("Failed to create libsoxr resampler context: %s.", (err ? err : "[unknown error]"));
> +        return -1;
> +    }
> +
> +    r->impl.free = resampler_soxr_free;
> +    r->impl.reset = resampler_soxr_reset;
> +    r->impl.update_rates = resampler_soxr_update_rates;
> +    r->impl.resample = resampler_soxr_resample;
> +    r->impl.data = state;
> +
> +    return 0;
> +}
> -- 
> 2.1.0
> 
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> 

-- 

Peter Meerwald
+43-664-2444418 (mobile)