add a software sample rate conversion feeder. this uses linear

interpolation for reasonable quality whilst not using too much cpu time.

sys/dev/sound/pcm/feeder_rate.c

@@ -0,0 +1,175 @@
+/*
+ * Copyright (c) 1999 Cameron Grant <gandalf@vilnya.demon.co.uk>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#include <dev/sound/pcm/sound.h>
+
+#include "feeder_if.h"
+
+MALLOC_DEFINE(M_RATEFEEDER, "ratefeed", "pcm rate feeder");
+
+#define FEEDBUFSZ	8192
+#undef FEEDER_DEBUG
+
+struct feed_rate_info {
+	u_int32_t src, dst;
+	int srcpos, srcinc;
+	int16_t *buffer;
+	u_int16_t alpha;
+};
+
+static int
+feed_rate_setup(struct pcm_feeder *f)
+{
+	struct feed_rate_info *info = f->data;
+
+	info->srcinc = (info->src << 16) / info->dst;
+	/* srcinc is 16.16 fixed point increment for srcpos for each dstpos */
+	info->srcpos = 0;
+	return 0;
+}
+
+static int
+feed_rate_set(struct pcm_feeder *f, int what, int value)
+{
+	struct feed_rate_info *info = f->data;
+
+	switch(what) {
+	case FEEDRATE_SRC:
+		info->src = value;
+		break;
+	case FEEDRATE_DST:
+		info->dst = value;
+		break;
+	default:
+		return -1;
+	}
+	return feed_rate_setup(f);
+}
+
+static int
+feed_rate_init(struct pcm_feeder *f)
+{
+	struct feed_rate_info *info;
+
+	info = malloc(sizeof(*info), M_RATEFEEDER, M_WAITOK | M_ZERO);
+	if (info == NULL)
+		return ENOMEM;
+	info->buffer = malloc(FEEDBUFSZ, M_RATEFEEDER, M_WAITOK | M_ZERO);
+	if (info->buffer == NULL) {
+		free(info, M_RATEFEEDER);
+		return ENOMEM;
+	}
+	info->src = DSP_DEFAULT_SPEED;
+	info->dst = DSP_DEFAULT_SPEED;
+	info->alpha = 0;
+	f->data = info;
+	return feed_rate_setup(f);
+}
+
+static int
+feed_rate_free(struct pcm_feeder *f)
+{
+	struct feed_rate_info *info = f->data;
+
+	if (info) {
+		if (info->buffer)
+			free(info->buffer, M_RATEFEEDER);
+		free(info, M_RATEFEEDER);
+	}
+	f->data = NULL;
+	return 0;
+}
+
+static int
+feed_rate(struct pcm_feeder *f, struct pcm_channel *c, u_int8_t *b, u_int32_t count, void *source)
+{
+	struct feed_rate_info *info = f->data;
+	int16_t *destbuf = (int16_t *)b;
+	int fetch, v, alpha, hidelta, spos, dpos;
+
+	/*
+	 * at this point:
+	 * info->srcpos is 24.8 fixed offset into the fetchbuffer.  0 <= srcpos <= 0xff
+	 *
+	 * our input and output are always AFMT_S16LE stereo.  this simplifies things.
+	 */
+
+	/*
+	 * we start by fetching enough source data into our buffer to generate
+	 * about as much as was requested.  we put it at offset 2 in the
+	 * buffer so that we can interpolate from the last samples in the
+	 * previous iteration- when we finish we will move our last samples
+	 * to the start of the buffer.
+	 */
+	spos = 0;
+	dpos = 0;
+
+	/* fetch is in bytes */
+	fetch = (count * info->srcinc) >> 16;
+	fetch = min(fetch, FEEDBUFSZ - 4) & ~3;
+	if (fetch == 0)
+		return 0;
+	fetch = FEEDER_FEED(f->source, c, ((u_int8_t *)info->buffer) + 4, fetch, source);
+	fetch /= 2;
+
+	alpha = info->alpha;
+	hidelta = min(info->srcinc >> 16, 1) * 2;
+	while ((spos + hidelta + 1) < fetch) {
+		v = (info->buffer[spos] * (0xffff - alpha)) + (info->buffer[spos + hidelta] * alpha);
+		destbuf[dpos++] = v >> 16;
+
+		v = (info->buffer[spos + 1] * (0xffff - alpha)) + (info->buffer[spos + hidelta + 1] * alpha);
+		destbuf[dpos++] = v >> 16;
+
+		alpha += info->srcinc;
+		spos += (alpha >> 16) * 2;
+		alpha &= 0xffff;
+
+	}
+	info->alpha = alpha & 0xffff;
+	info->buffer[0] = info->buffer[spos - hidelta];
+	info->buffer[1] = info->buffer[spos - hidelta + 1];
+
+	count = dpos * 2;
+	return count;
+}
+
+static struct pcm_feederdesc feeder_rate_desc[] = {
+	{FEEDER_RATE, AFMT_S16_LE | AFMT_STEREO, AFMT_S16_LE | AFMT_STEREO, 0},
+	{0},
+};
+static kobj_method_t feeder_rate_methods[] = {
+    	KOBJMETHOD(feeder_init,		feed_rate_init),
+    	KOBJMETHOD(feeder_free,		feed_rate_free),
+    	KOBJMETHOD(feeder_set,		feed_rate_set),
+    	KOBJMETHOD(feeder_feed,		feed_rate),
+	{ 0, 0 }
+};
+FEEDER_DECLARE(feeder_rate, 2, NULL);
+
+