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author | cg <cg@FreeBSD.org> | 2001-04-08 20:26:22 +0000 |
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committer | cg <cg@FreeBSD.org> | 2001-04-08 20:26:22 +0000 |
commit | 1c1d868e786417d56cdae2344a3cd0d71f032765 (patch) | |
tree | 86feb88d5cbc3f4febc9872c269b046f775f9770 | |
parent | f9db4ec2f7caac8d7765b3c64c6f06f9fe0e01df (diff) | |
download | FreeBSD-src-1c1d868e786417d56cdae2344a3cd0d71f032765.zip FreeBSD-src-1c1d868e786417d56cdae2344a3cd0d71f032765.tar.gz |
add a software sample rate conversion feeder. this uses linear
interpolation for reasonable quality whilst not using too much cpu time.
-rw-r--r-- | sys/dev/sound/pcm/feeder_rate.c | 175 |
1 files changed, 175 insertions, 0 deletions
diff --git a/sys/dev/sound/pcm/feeder_rate.c b/sys/dev/sound/pcm/feeder_rate.c new file mode 100644 index 0000000..936e85f --- /dev/null +++ b/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); + + |