/*

 * Rate converter plugin using libavresample

 * Copyright (c) 2014 by Anton Khirnov

 *

 * This library 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.

 *

 * This library 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

 * Lesser General Public License for more details.

 */

#include <stdio.h>

#include <alsa/asoundlib.h>

#include <alsa/pcm_rate.h>

#include <libavresample/avresample.h>

#include <libavutil/channel_layout.h>

#include <libavutil/opt.h>

#include <libavutil/mathematics.h>

#include <libavutil/samplefmt.h>

static unsigned int filter_size = 16;

static unsigned int phase_shift = 10; /* auto-adjusts */

static double cutoff = 0; /* auto-adjusts */

struct rate_src {

	AVAudioResampleContext *avr;

	unsigned int in_rate;

	unsigned int out_rate;

	unsigned int channels;

};

static snd_pcm_uframes_t input_frames(void *obj ATTRIBUTE_UNUSED,

				      snd_pcm_uframes_t frames)

{

	return frames;

}

static snd_pcm_uframes_t output_frames(void *obj ATTRIBUTE_UNUSED,

				       snd_pcm_uframes_t frames)

{

	return frames;

}

static void pcm_src_free(void *obj)

{

	struct rate_src *rate = obj;

	avresample_free(&rate->avr);

}

static int pcm_src_init(void *obj, snd_pcm_rate_info_t *info)

{

	struct rate_src *rate = obj;

	int i, ir, or;

	if (!rate->avr || rate->channels != info->channels) {

		int ret;

		pcm_src_free(rate);

		rate->channels = info->channels;

		ir = rate->in_rate = info->in.rate;

		or = rate->out_rate = info->out.rate;

		i = av_gcd(or, ir);

		if (or > ir) {

			phase_shift = or/i;

		} else {

			phase_shift = ir/i;

		}

		if (cutoff <= 0.0) {

			cutoff = 1.0 - 1.0/filter_size;

			if (cutoff < 0.80)

				cutoff = 0.80;

		}

		rate->avr = avresample_alloc_context();

		if (!rate->avr)

			return -ENOMEM;

		av_opt_set_int(rate->avr, "in_sample_rate",     info->in.rate,  0);

		av_opt_set_int(rate->avr, "out_sample_rate",    info->out.rate, 0);

		av_opt_set_int(rate->avr, "in_sample_format",   AV_SAMPLE_FMT_S16, 0);

		av_opt_set_int(rate->avr, "out_sample_format",  AV_SAMPLE_FMT_S16, 0);

		av_opt_set_int(rate->avr, "in_channel_layout",  av_get_default_channel_layout(rate->channels), 0);

		av_opt_set_int(rate->avr, "out_channel_layout", av_get_default_channel_layout(rate->channels), 0);

		av_opt_set_int(rate->avr, "filter_size",        filter_size, 0);

		av_opt_set_int(rate->avr, "phase_shift",        phase_shift, 0);

		av_opt_set_double(rate->avr, "cutoff",          cutoff,      0);

		ret = avresample_open(rate->avr);

		if (ret < 0) {

			avresample_free(&rate->avr);

			return -EINVAL;

		}

	}

	return 0;

}

static int pcm_src_adjust_pitch(void *obj, snd_pcm_rate_info_t *info)

{

	struct rate_src *rate = obj;

	if (info->out.rate != rate->out_rate || info->in.rate != rate->in_rate)

		pcm_src_init(obj, info);

	return 0;

}

static void pcm_src_reset(void *obj)

{

	struct rate_src *rate = obj;

	if (rate->avr) {

#if 0

		avresample_close(rate->avr);

		avresample_open(rate->avr);

#endif

	}

}

static void pcm_src_convert_s16(void *obj, int16_t *dst,

				unsigned int dst_frames,

				const int16_t *src,

				unsigned int src_frames)

{

	struct rate_src *rate = obj;

	int chans = rate->channels;

	unsigned int total_in = avresample_get_delay(rate->avr) + src_frames;

	avresample_convert(rate->avr, (uint8_t **)&dst, dst_frames * chans * 2, dst_frames,

	                   (uint8_t **)&src, src_frames * chans * 2, src_frames);

	avresample_set_compensation(rate->avr,

                                    total_in - src_frames > filter_size ? 0 : 1, src_frames);

}

static void pcm_src_close(void *obj)

{

	pcm_src_free(obj);

}

#if SND_PCM_RATE_PLUGIN_VERSION >= 0x010002

static int get_supported_rates(void *obj ATTRIBUTE_UNUSED,

			       unsigned int *rate_min,

			       unsigned int *rate_max)

{

	*rate_min = *rate_max = 0; /* both unlimited */

	return 0;

}

static void dump(void *obj ATTRIBUTE_UNUSED, snd_output_t *out)

{

	snd_output_printf(out, "Converter: libavr\n");

}

#endif

static snd_pcm_rate_ops_t pcm_src_ops = {

	.close = pcm_src_close,

	.init = pcm_src_init,

	.free = pcm_src_free,

	.reset = pcm_src_reset,

	.adjust_pitch = pcm_src_adjust_pitch,

	.convert_s16 = pcm_src_convert_s16,

	.input_frames = input_frames,

	.output_frames = output_frames,

#if SND_PCM_RATE_PLUGIN_VERSION >= 0x010002

	.version = SND_PCM_RATE_PLUGIN_VERSION,

	.get_supported_rates = get_supported_rates,

	.dump = dump,

#endif

};

int pcm_src_open(unsigned int version, void **objp, snd_pcm_rate_ops_t *ops)

{

	struct rate_src *rate;

#if SND_PCM_RATE_PLUGIN_VERSION < 0x010002

	if (version != SND_PCM_RATE_PLUGIN_VERSION) {

		fprintf(stderr, "Invalid rate plugin version %x\n", version);

		return -EINVAL;

	}

#endif

	rate = calloc(1, sizeof(*rate));

	if (!rate)

		return -ENOMEM;

	*objp = rate;

	rate->avr = NULL;

#if SND_PCM_RATE_PLUGIN_VERSION >= 0x010002

	if (version == 0x010001)

		memcpy(ops, &pcm_src_ops, sizeof(snd_pcm_rate_old_ops_t));

	else

#endif

		*ops = pcm_src_ops;

	return 0;

}

int SND_PCM_RATE_PLUGIN_ENTRY(lavrate)(unsigned int version, void **objp,

			snd_pcm_rate_ops_t *ops)

{

	return pcm_src_open(version, objp, ops);

}

int SND_PCM_RATE_PLUGIN_ENTRY(lavrate_higher)(unsigned int version,

			void **objp, snd_pcm_rate_ops_t *ops)

{

	filter_size = 64;

	return pcm_src_open(version, objp, ops);

}

int SND_PCM_RATE_PLUGIN_ENTRY(lavrate_high)(unsigned int version,

			void **objp, snd_pcm_rate_ops_t *ops)

{

	filter_size = 32;

	return pcm_src_open(version, objp, ops);

}

int SND_PCM_RATE_PLUGIN_ENTRY(lavrate_fast)(unsigned int version,

			void **objp, snd_pcm_rate_ops_t *ops)

{

	filter_size = 8;

	return pcm_src_open(version, objp, ops);

}

int SND_PCM_RATE_PLUGIN_ENTRY(lavrate_faster)(unsigned int version,

			void **objp, snd_pcm_rate_ops_t *ops)

{

	filter_size = 4;

	return pcm_src_open(version, objp, ops);

}