HomoFast-eSpeak-Persian/src/libespeak-ng/wave_pulse.c

/*
 * Copyright (C) 2007, Gilles Casse <[email protected]>
 * Copyright (C) 2015 Reece H. Dunn
 * eSpeak driver for PulseAudio
 * based on the XMMS PulseAudio Plugin
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License
 * along with this program; if not, see: <http://www.gnu.org/licenses/>.
 */

// TBD:
// * ARCH_BIG
// * uint64? a_timing_info.read_index
// * prebuf,... size?
// * 0.9.6: pb pulse_free using tlength=8820 (max size never returned -> tlength=10000 ok, but higher drain).
//
#include "speech.h"

#ifdef USE_ASYNC
// This source file is only used for asynchronious modes

#include <stdbool.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <assert.h>
#include <sys/time.h>
#include <time.h>
#include <pulse/pulseaudio.h>
#include <pthread.h>

#ifndef PLATFORM_WINDOWS
#include <unistd.h>
#endif
#include "wave.h"
#include "debug.h"

enum {ONE_BILLION=1000000000};

enum {
	/* return value */
	PULSE_OK = 0,
	PULSE_ERROR = -1,
	PULSE_NO_CONNECTION = -2
};

#ifdef USE_PULSEAUDIO

static t_wave_callback* my_callback_is_output_enabled=NULL;

#define SAMPLE_RATE 22050
#define ESPEAK_FORMAT PA_SAMPLE_S16LE
#define ESPEAK_CHANNEL 1

#define MAXLENGTH 132300
#define TLENGTH 4410
#define PREBUF 2200
#define MINREQ 880
#define FRAGSIZE 0

#ifdef USE_PORTAUDIO
// rename functions to be wrapped
#define wave_init wave_pulse_init
#define wave_open wave_pulse_open
#define wave_write wave_pulse_write
#define wave_close wave_pulse_close
#define wave_is_busy wave_pulse_is_busy
#define wave_terminate wave_pulse_terminate
#define wave_get_read_position wave_pulse_get_read_position
#define wave_get_write_position wave_pulse_get_write_position
#define wave_flush wave_pulse_flush
#define wave_set_callback_is_output_enabled wave_pulse_set_callback_is_output_enabled
#define wave_test_get_write_buffer wave_pulse_test_get_write_buffer
#define wave_get_remaining_time wave_pulse_get_remaining_time

// check whether we can connect to PulseAudio
#include <pulse/simple.h>
int is_pulse_running()
{
	pa_sample_spec ss;
	ss.format = ESPEAK_FORMAT;
	ss.rate = SAMPLE_RATE;
	ss.channels = ESPEAK_CHANNEL;

	pa_simple *s = pa_simple_new(NULL, "eSpeak", PA_STREAM_PLAYBACK, NULL, "is_pulse_running", &ss, NULL, NULL, NULL);
	if (s) {
		pa_simple_free(s);
		return 1;
	} else
		return 0;
}
#endif // USE_PORTAUDIO

static pthread_mutex_t pulse_mutex;

static pa_context *context = NULL;
static pa_stream *stream = NULL;
static pa_threaded_mainloop *mainloop = NULL;

static int do_trigger = 0;
static uint64_t written = 0;
static int time_offset_msec = 0;
static int just_flushed = 0;

static int connected = 0;
static int wave_samplerate;

#define CHECK_DEAD_GOTO(label, warn) do { \
		if (!mainloop || \
		    !context || pa_context_get_state(context) != PA_CONTEXT_READY || \
		    !stream || pa_stream_get_state(stream) != PA_STREAM_READY) { \
			if (warn) \
				SHOW("Connection died: %s\n", context ? pa_strerror(pa_context_errno(context)) : "NULL"); \
			goto label; \
		}  \
} while(0);

#define CHECK_CONNECTED(retval) \
	do { \
		if (!connected) return retval; \
	} while (0);

#define CHECK_CONNECTED_NO_RETVAL(id)                   \
	do {                                  \
		if (!connected) { SHOW("CHECK_CONNECTED_NO_RETVAL: !pulse_connected\n", ""); return; } \
	} while (0);

static void subscribe_cb(struct pa_context *c, enum pa_subscription_event_type t, uint32_t index, void *userdata) {
	ENTER(__FUNCTION__);

	assert(c);

	if (!stream ||
	    index != pa_stream_get_index(stream) ||
	    (t != (PA_SUBSCRIPTION_EVENT_SINK_INPUT|PA_SUBSCRIPTION_EVENT_CHANGE) &&
	     t != (PA_SUBSCRIPTION_EVENT_SINK_INPUT|PA_SUBSCRIPTION_EVENT_NEW)))
		return;
}

static void context_state_cb(pa_context *c, void *userdata) {
	ENTER(__FUNCTION__);
	assert(c);

	switch (pa_context_get_state(c)) {
	case PA_CONTEXT_READY:
	case PA_CONTEXT_TERMINATED:
	case PA_CONTEXT_FAILED:
		pa_threaded_mainloop_signal(mainloop, 0);
		break;

	case PA_CONTEXT_UNCONNECTED:
	case PA_CONTEXT_CONNECTING:
	case PA_CONTEXT_AUTHORIZING:
	case PA_CONTEXT_SETTING_NAME:
		break;
	}
}

static void stream_state_cb(pa_stream *s, void * userdata) {
	ENTER(__FUNCTION__);
	assert(s);

	switch (pa_stream_get_state(s)) {

	case PA_STREAM_READY:
	case PA_STREAM_FAILED:
	case PA_STREAM_TERMINATED:
		pa_threaded_mainloop_signal(mainloop, 0);
		break;

	case PA_STREAM_UNCONNECTED:
	case PA_STREAM_CREATING:
		break;
	}
}

static void stream_success_cb(pa_stream *s, int success, void *userdata) {
	ENTER(__FUNCTION__);
	assert(s);

	if (userdata)
		*(int*) userdata = success;

	pa_threaded_mainloop_signal(mainloop, 0);
}

static void context_success_cb(pa_context *c, int success, void *userdata) {
	ENTER(__FUNCTION__);
	assert(c);

	if (userdata)
		*(int*) userdata = success;

	pa_threaded_mainloop_signal(mainloop, 0);
}

static void stream_request_cb(pa_stream *s, size_t length, void *userdata) {
	ENTER(__FUNCTION__);
	assert(s);

	pa_threaded_mainloop_signal(mainloop, 0);
}

static void stream_latency_update_cb(pa_stream *s, void *userdata) {
	assert(s);

	pa_threaded_mainloop_signal(mainloop, 0);
}

static int pulse_free(void) {
	ENTER(__FUNCTION__);
	size_t l = 0;
	pa_operation *o = NULL;

	CHECK_CONNECTED(0);

	SHOW("pulse_free: %s (call)\n", "pa_threaded_main_loop_lock");
	pa_threaded_mainloop_lock(mainloop);
	CHECK_DEAD_GOTO(fail, 1);

	if ((l = pa_stream_writable_size(stream)) == (size_t) -1) {
		SHOW("pa_stream_writable_size() failed: %s", pa_strerror(pa_context_errno(context)));
		l = 0;
		goto fail;
	}

	SHOW("pulse_free: %s (ret=%d)\n", "pa_stream_writable_size", l);

	/* If this function is called twice with no pulse_write() call in
	 * between this means we should trigger the playback */
	if (do_trigger) {
		int success = 0;

		SHOW("pulse_free: %s (call)\n", "pa_stream_trigger");
		if (!(o = pa_stream_trigger(stream, stream_success_cb, &success))) {
			SHOW("pa_stream_trigger() failed: %s", pa_strerror(pa_context_errno(context)));
			goto fail;
		}

		SHOW("pulse_free: %s (call)\n", "pa_threaded_main_loop");
		while (pa_operation_get_state(o) != PA_OPERATION_DONE) {
			CHECK_DEAD_GOTO(fail, 1);
			pa_threaded_mainloop_wait(mainloop);
		}
		SHOW("pulse_free: %s (ret)\n", "pa_threaded_main_loop");

		if (!success)
			SHOW("pa_stream_trigger() failed: %s", pa_strerror(pa_context_errno(context)));
	}

fail:
	SHOW("pulse_free: %s (call)\n", "pa_operation_unref");
	if (o)
		pa_operation_unref(o);

	SHOW("pulse_free: %s (call)\n", "pa_threaded_main_loop_unlock");
	pa_threaded_mainloop_unlock(mainloop);

	do_trigger = !!l;
	SHOW("pulse_free: %d (ret)\n", (int)l);
	return (int) l;
}

static int pulse_playing(const pa_timing_info *the_timing_info) {
	ENTER(__FUNCTION__);
	int r = 0;
	const pa_timing_info *i;

	assert(the_timing_info);

	CHECK_CONNECTED(0);

	pa_threaded_mainloop_lock(mainloop);

	for (;; ) {
		CHECK_DEAD_GOTO(fail, 1);

		if ((i = pa_stream_get_timing_info(stream)))
		{
			break;
		}
		if (pa_context_errno(context) != PA_ERR_NODATA) {
			SHOW("pa_stream_get_timing_info() failed: %s", pa_strerror(pa_context_errno(context)));
			goto fail;
		}

		pa_threaded_mainloop_wait(mainloop);
	}

	r = i->playing;
	memcpy((void*)the_timing_info, (void*)i, sizeof(pa_timing_info));

fail:
	pa_threaded_mainloop_unlock(mainloop);

	return r;
}

static void pulse_write(void* ptr, int length) {
	ENTER(__FUNCTION__);


	SHOW("pulse_write > length=%d\n", length);

	CHECK_CONNECTED_NO_RETVAL();

	pa_threaded_mainloop_lock(mainloop);
	CHECK_DEAD_GOTO(fail, 1);

	if (pa_stream_write(stream, ptr, length, NULL, PA_SEEK_RELATIVE, (pa_seek_mode_t)0) < 0) {
		SHOW("pa_stream_write() failed: %s", pa_strerror(pa_context_errno(context)));
		goto fail;
	}

	do_trigger = 0;
	written += length;

fail:

	pa_threaded_mainloop_unlock(mainloop);
}

static int drain(void) {
	pa_operation *o = NULL;
	int success = 0;
	int ret = PULSE_ERROR;

	ENTER(__FUNCTION__);

	CHECK_CONNECTED(ret);

	pa_threaded_mainloop_lock(mainloop);
	CHECK_DEAD_GOTO(fail, 0);

	SHOW_TIME("pa_stream_drain (call)");
	if (!(o = pa_stream_drain(stream, stream_success_cb, &success))) {
		SHOW("pa_stream_drain() failed: %s\n", pa_strerror(pa_context_errno(context)));
		goto fail;
	}

	SHOW_TIME("pa_threaded_mainloop_wait (call)");
	while (pa_operation_get_state(o) != PA_OPERATION_DONE) {
		CHECK_DEAD_GOTO(fail, 1);
		pa_threaded_mainloop_wait(mainloop);
	}
	SHOW_TIME("pa_threaded_mainloop_wait (ret)");

	if (!success) {
		SHOW("pa_stream_drain() failed: %s\n", pa_strerror(pa_context_errno(context)));
	}
	else {
		ret = PULSE_OK;
	}

fail:
	SHOW_TIME("pa_operation_unref (call)");
	if (o)
		pa_operation_unref(o);

	pa_threaded_mainloop_unlock(mainloop);
	SHOW_TIME("drain (ret)");

	return ret;
}


static void pulse_close(void) {

	ENTER(__FUNCTION__);

	drain();

	connected = 0;

	if (mainloop)
		pa_threaded_mainloop_stop(mainloop);

	connected = 0;

	if (context) {
		SHOW_TIME("pa_context_disconnect (call)");
		pa_context_disconnect(context);
		pa_context_unref(context);
		context = NULL;
	}

	if (mainloop) {
		SHOW_TIME("pa_threaded_mainloop_free (call)");
		pa_threaded_mainloop_free(mainloop);
		mainloop = NULL;
	}
	SHOW_TIME("pulse_close (ret)");

}


static int pulse_open()
{
	ENTER(__FUNCTION__);
	pa_sample_spec ss;
	pa_operation *o = NULL;
	int success;
	int ret = PULSE_ERROR;

	assert(!mainloop);
	assert(!context);
	assert(!stream);
	assert(!connected);

	pthread_mutex_init( &pulse_mutex, (const pthread_mutexattr_t *)NULL);

	ss.format = ESPEAK_FORMAT;
	ss.rate = wave_samplerate;
	ss.channels = ESPEAK_CHANNEL;

	if (!pa_sample_spec_valid(&ss))
		return false;

	SHOW_TIME("pa_threaded_mainloop_new (call)");
	if (!(mainloop = pa_threaded_mainloop_new())) {
		SHOW("Failed to allocate main loop\n","");
		goto fail;
	}

	pa_threaded_mainloop_lock(mainloop);

	SHOW_TIME("pa_context_new (call)");
	if (!(context = pa_context_new(pa_threaded_mainloop_get_api(mainloop), "eSpeak"))) {
		SHOW("Failed to allocate context\n","");
		goto unlock_and_fail;
	}

	pa_context_set_state_callback(context, context_state_cb, NULL);
	pa_context_set_subscribe_callback(context, subscribe_cb, NULL);

	SHOW_TIME("pa_context_connect (call)");
	if (pa_context_connect(context, NULL, (pa_context_flags_t)0, NULL) < 0) {
		SHOW("Failed to connect to server: %s", pa_strerror(pa_context_errno(context)));
		ret = PULSE_NO_CONNECTION;
		goto unlock_and_fail;
	}

	SHOW_TIME("pa_threaded_mainloop_start (call)");
	if (pa_threaded_mainloop_start(mainloop) < 0) {
		SHOW("Failed to start main loop","");
		goto unlock_and_fail;
	}

	/* Wait until the context is ready */
	SHOW_TIME("pa_threaded_mainloop_wait");
	pa_threaded_mainloop_wait(mainloop);

	if (pa_context_get_state(context) != PA_CONTEXT_READY) {
		SHOW("Failed to connect to server: %s", pa_strerror(pa_context_errno(context)));
		ret = PULSE_NO_CONNECTION;
		if (mainloop)
			pa_threaded_mainloop_stop(mainloop);
		goto unlock_and_fail;
	}

	SHOW_TIME("pa_stream_new");
	if (!(stream = pa_stream_new(context, "unknown", &ss, NULL))) {
		SHOW("Failed to create stream: %s", pa_strerror(pa_context_errno(context)));
		goto unlock_and_fail;
	}

	pa_stream_set_state_callback(stream, stream_state_cb, NULL);
	pa_stream_set_write_callback(stream, stream_request_cb, NULL);
	pa_stream_set_latency_update_callback(stream, stream_latency_update_cb, NULL);

	pa_buffer_attr a_attr;

	a_attr.maxlength = MAXLENGTH;
	a_attr.tlength = TLENGTH;
	a_attr.prebuf = PREBUF;
	a_attr.minreq = MINREQ;
	a_attr.fragsize = 0;

	SHOW_TIME("pa_connect_playback");
	if (pa_stream_connect_playback(stream, NULL, &a_attr, (pa_stream_flags_t)(PA_STREAM_INTERPOLATE_TIMING|PA_STREAM_AUTO_TIMING_UPDATE), NULL, NULL) < 0) {
		SHOW("Failed to connect stream: %s", pa_strerror(pa_context_errno(context)));
		goto unlock_and_fail;
	}

	/* Wait until the stream is ready */
	SHOW_TIME("pa_threaded_mainloop_wait");
	pa_threaded_mainloop_wait(mainloop);

	if (pa_stream_get_state(stream) != PA_STREAM_READY) {
		SHOW("Failed to connect stream: %s", pa_strerror(pa_context_errno(context)));
		goto unlock_and_fail;
	}

	/* Now subscribe to events */
	SHOW_TIME("pa_context_subscribe");
	if (!(o = pa_context_subscribe(context, PA_SUBSCRIPTION_MASK_SINK_INPUT, context_success_cb, &success))) {
		SHOW("pa_context_subscribe() failed: %s", pa_strerror(pa_context_errno(context)));
		goto unlock_and_fail;
	}

	success = 0;
	SHOW_TIME("pa_threaded_mainloop_wait");
	while (pa_operation_get_state(o) != PA_OPERATION_DONE) {
		CHECK_DEAD_GOTO(fail, 1);
		pa_threaded_mainloop_wait(mainloop);
	}

	pa_operation_unref(o);

	if (!success) {
		SHOW("pa_context_subscribe() failed: %s", pa_strerror(pa_context_errno(context)));
		goto unlock_and_fail;
	}

	do_trigger = 0;
	written = 0;
	time_offset_msec = 0;
	just_flushed = 0;
	connected = 1;

	pa_threaded_mainloop_unlock(mainloop);
	SHOW_TIME("pulse_open (ret true)");

	return PULSE_OK;

unlock_and_fail:

	if (o)
		pa_operation_unref(o);

	pa_threaded_mainloop_unlock(mainloop);

fail:

	if (ret == PULSE_NO_CONNECTION) {
		if (context) {
			SHOW_TIME("pa_context_disconnect (call)");
			pa_context_disconnect(context);
			pa_context_unref(context);
			context = NULL;
		}

		if (mainloop) {
			SHOW_TIME("pa_threaded_mainloop_free (call)");
			pa_threaded_mainloop_free(mainloop);
			mainloop = NULL;
		}
	}
	else {
		pulse_close();
	}

	SHOW_TIME("pulse_open (ret false)");

	return ret;

}

void wave_flush(void* theHandler)
{
	ENTER("wave_flush");
}

void wave_set_callback_is_output_enabled(t_wave_callback* cb)
{
	my_callback_is_output_enabled = cb;
}

int wave_init(int srate)
{
	ENTER("wave_init");

	stream = NULL;
	wave_samplerate = srate;

	return pulse_open() == PULSE_OK;
}

void* wave_open(const char* the_api)
{
	ENTER("wave_open");
	return((void*)1);
}

size_t wave_write(void* theHandler, char* theMono16BitsWaveBuffer, size_t theSize)
{
	ENTER("wave_write");
	size_t bytes_to_write = theSize;
	char* aBuffer=theMono16BitsWaveBuffer;

	assert(stream);

	size_t aTotalFreeMem=0;

	pthread_mutex_lock(&pulse_mutex);

	while (1)
	{
		if (my_callback_is_output_enabled
		    && (0==my_callback_is_output_enabled()))
		{
			SHOW_TIME("wave_write > my_callback_is_output_enabled: no!");
			theSize=0;
			goto terminate;
		}

		aTotalFreeMem = pulse_free();
		if (aTotalFreeMem >= bytes_to_write)
		{
			SHOW("wave_write > aTotalFreeMem(%d) >= bytes_to_write(%d)\n", aTotalFreeMem, bytes_to_write);
			break;
		}

		// TBD: check if really helpful
		if (aTotalFreeMem >= MAXLENGTH*2)
		{
			aTotalFreeMem = MAXLENGTH*2;
		}

		SHOW("wave_write > wait: aTotalFreeMem(%d) < bytes_to_write(%d)\n", aTotalFreeMem, bytes_to_write);

		// 500: threshold for avoiding too many calls to pulse_write
		if (aTotalFreeMem>500)
		{
			pulse_write(aBuffer, aTotalFreeMem);
			bytes_to_write -= aTotalFreeMem;
			aBuffer += aTotalFreeMem;
		}

		usleep(10000);
	}

	pulse_write(aBuffer, bytes_to_write);

terminate:
	pthread_mutex_unlock(&pulse_mutex);
	SHOW("wave_write: theSize=%d", theSize);
	SHOW_TIME("wave_write > LEAVE");
	return theSize;
}

int wave_close(void* theHandler)
{
	SHOW_TIME("wave_close > ENTER");
	static int aStopStreamCount = 0;

	// Avoid race condition by making sure this function only
	// gets called once at a time
	aStopStreamCount++;
	if (aStopStreamCount != 1)
	{
		SHOW_TIME("wave_close > LEAVE (stopStreamCount)");
		return 0;
	}

	int a_status = pthread_mutex_lock(&pulse_mutex);
	if (a_status)
	{
		SHOW("Error: pulse_mutex lock=%d (%s)\n", a_status, __FUNCTION__);
		aStopStreamCount = 0; // last action
		return PULSE_ERROR;
	}

	drain();

	pthread_mutex_unlock(&pulse_mutex);
	SHOW_TIME("wave_close (ret)");

	aStopStreamCount = 0; // last action
	return PULSE_OK;
}

int wave_is_busy(void* theHandler)
{
	SHOW_TIME("wave_is_busy");

	pa_timing_info a_timing_info;
	int active = pulse_playing(&a_timing_info);
	SHOW("wave_is_busy: %d\n",active);
	return active;
}

void wave_terminate()
{
	ENTER("wave_terminate");

	int a_status;
	pthread_mutex_t* a_mutex = NULL;
	a_mutex = &pulse_mutex;
	a_status = pthread_mutex_lock(a_mutex);

	pulse_close();

	SHOW_TIME("unlock mutex");
	a_status = pthread_mutex_unlock(a_mutex);
	pthread_mutex_destroy(a_mutex);
}

uint32_t wave_get_read_position(void* theHandler)
{
	pa_timing_info a_timing_info;
	pulse_playing(&a_timing_info);
	SHOW("wave_get_read_position > %lx\n", a_timing_info.read_index);
	return a_timing_info.read_index;
}

uint32_t wave_get_write_position(void* theHandler)
{
	pa_timing_info a_timing_info;
	pulse_playing(&a_timing_info);
	SHOW("wave_get_read_position > %lx\n", a_timing_info.write_index);
	return a_timing_info.write_index;
}

int wave_get_remaining_time(uint32_t sample, uint32_t* time)
{
	double a_time=0;

	if (!time || !stream)
	{
		SHOW("event get_remaining_time> %s\n","audio device not available");
		return -1;
	}

	pa_timing_info a_timing_info;
	pulse_playing(&a_timing_info);

	if (sample > a_timing_info.read_index)
	{
		// TBD: take in account time suplied by portaudio V18 API
		a_time = sample - a_timing_info.read_index;
		a_time = 0.5 + (a_time * 1000.0) / wave_samplerate;
	}
	else
	{
		a_time = 0;
	}

	SHOW("wave_get_remaining_time > sample=%d, time=%d\n", sample, (uint32_t)a_time);

	*time = (uint32_t)a_time;

	return 0;
}

void *wave_test_get_write_buffer()
{
	return NULL;
}


#else


int wave_init(return 1; ) {
}
void* wave_open(const char* the_api) {
	return (void *)1;
}
size_t wave_write(void* theHandler, char* theMono16BitsWaveBuffer, size_t theSize) {
	return theSize;
}
int wave_close(void* theHandler) {
	return 0;
}
int wave_is_busy(void* theHandler) {
	return 0;
}
void wave_terminate() {
}
uint32_t wave_get_read_position(void* theHandler) {
	return 0;
}
uint32_t wave_get_write_position(void* theHandler) {
	return 0;
}
void wave_flush(void* theHandler) {
}
typedef int (t_wave_callback)(void);
void wave_set_callback_is_output_enabled(t_wave_callback* cb) {
}
extern void* wave_test_get_write_buffer() {
	return NULL;
}

int wave_get_remaining_time(uint32_t sample, uint32_t* time)
{
	if (!time) return(-1);
	*time = (uint32_t)0;
	return 0;
}

#endif  // of USE_PULSEAUDIO

#ifndef USE_PORTAUDIO

void clock_gettime2(struct timespec *ts)
{
	struct timeval tv;

	if (!ts)
	{
		return;
	}

	assert (gettimeofday(&tv, NULL) != -1);
	ts->tv_sec = tv.tv_sec;
	ts->tv_nsec = tv.tv_usec*1000;
}

void add_time_in_ms(struct timespec *ts, int time_in_ms)
{
	if (!ts)
	{
		return;
	}

	uint64_t t_ns = (uint64_t)ts->tv_nsec + 1000000 * (uint64_t)time_in_ms;
	while(t_ns >= ONE_BILLION)
	{
		SHOW("event > add_time_in_ms ns: %d sec %Lu nsec \n", ts->tv_sec, t_ns);
		ts->tv_sec += 1;
		t_ns -= ONE_BILLION;
	}
	ts->tv_nsec = (long int)t_ns;
}
#endif  // ifndef USE_PORTAUDIO


#endif   // USE_ASYNC