resample_resample.c

一个开源的sip源代码

/* $Id: resample_resample.c 1266 2007-05-11 15:14:34Z bennylp $ */
/* 
 * Copyright (C) 2003-2007 Benny Prijono <[e-mail]>
 *
 * 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 2 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, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 
 */

#include <pjmedia/resample.h>

#include <pjmedia/errno.h>
#include <pj/assert.h>
#include <pj/log.h>
#include <pj/pool.h>


#if defined(PJMEDIA_HAS_LIBRESAMPLE) && PJMEDIA_HAS_LIBRESAMPLE != 0

#include <third_party/resample/include/resamplesubs.h>

#define THIS_FILE   "resample.c"



struct pjmedia_resample
{
    double	 factor;	/* Conversion factor = rate_out / rate_in.  */
    pj_bool_t	 large_filter;	/* Large filter?			    */
    pj_bool_t	 high_quality;	/* Not fast?				    */
    unsigned	 xoff;		/* History and lookahead size, in samples   */
    unsigned	 frame_size;	/* Samples per frame.			    */
    pj_int16_t	*buffer;	/* Input buffer.			    */
};


PJ_DEF(pj_status_t) pjmedia_resample_create( pj_pool_t *pool,
					     pj_bool_t high_quality,
					     pj_bool_t large_filter,
					     unsigned channel_count,
					     unsigned rate_in,
					     unsigned rate_out,
					     unsigned samples_per_frame,
					     pjmedia_resample **p_resample)
{
    pjmedia_resample *resample;

    PJ_ASSERT_RETURN(pool && p_resample && rate_in &&
		     rate_out && samples_per_frame, PJ_EINVAL);

    resample = PJ_POOL_ALLOC_T(pool, pjmedia_resample);
    PJ_ASSERT_RETURN(resample, PJ_ENOMEM);

    PJ_UNUSED_ARG(channel_count);

    /*
     * If we're downsampling, always use the fast algorithm since it seems
     * to yield the same quality.
     */
    if (rate_out < rate_in) {
	//no this is not a good idea. It sounds pretty good with speech,
	//but very poor with background noise etc.
	//high_quality = 0;
    }

    resample->factor = rate_out * 1.0 / rate_in;
    resample->large_filter = large_filter;
    resample->high_quality = high_quality;
    resample->frame_size = samples_per_frame;

    if (high_quality) {
	unsigned size;

	/* This is a bug in xoff calculation, thanks Stephane Lussier
	 * of Macadamian dot com.
	 *   resample->xoff = large_filter ? 32 : 6;
	 */
	resample->xoff = res_GetXOFF(resample->factor, (char)large_filter);

	size = (samples_per_frame + 2*resample->xoff) * sizeof(pj_int16_t);
	resample->buffer = (pj_int16_t*) pj_pool_alloc(pool, size);
	PJ_ASSERT_RETURN(resample->buffer, PJ_ENOMEM);

	pjmedia_zero_samples(resample->buffer, resample->xoff*2);


    } else {
	resample->xoff = 0;
    }

    *p_resample = resample;

    PJ_LOG(5,(THIS_FILE, "resample created: %s qualiy, %s filter, in/out "
			  "rate=%d/%d", 
			  (high_quality?"high":"low"),
			  (large_filter?"large":"small"),
			  rate_in, rate_out));
    return PJ_SUCCESS;
}



PJ_DEF(void) pjmedia_resample_run( pjmedia_resample *resample,
				   const pj_int16_t *input,
				   pj_int16_t *output )
{
    PJ_ASSERT_ON_FAIL(resample, return);

    if (resample->high_quality) {
	pj_int16_t *dst_buf;
	const pj_int16_t *src_buf;

	/* Okay chaps, here's how we do resampling.
	 *
	 * The original resample algorithm requires xoff samples *before* the
	 * input buffer as history, and another xoff samples *after* the
	 * end of the input buffer as lookahead. Since application can only
	 * supply framesize buffer on each run, PJMEDIA needs to arrange the
	 * buffer to meet these requirements.
	 *
	 * So here comes the trick.
	 *
	 * First of all, because of the history and lookahead requirement, 
	 * resample->buffer need to accomodate framesize+2*xoff samples in its
	 * buffer. This is done when the buffer is created.
	 *
	 * On the first run, the input frame (supplied by application) is
	 * copied to resample->buffer at 2*xoff position. The first 2*xoff
	 * samples are initially zeroed (in the initialization). The resample
	 * algorithm then invoked at resample->buffer+xoff ONLY, thus giving
	 * it one xoff at the beginning as zero, and one xoff at the end
	 * as the end of the original input. The resample algorithm will see
	 * that the first xoff samples in the input as zero.
	 *
	 * So here's the layout of resample->buffer on the first run.
	 *
	 * run 0 
	 *     +------+------+--------------+
	 *     | 0000 | 0000 |  frame0...   |
	 *     +------+------+--------------+
	 *     ^      ^      ^              ^
         *     0    xoff  2*xoff       size+2*xoff 
         *
	 * (Note again: resample algorithm is called at resample->buffer+xoff)
	 *
	 * At the end of the run, 2*xoff samples from the end of 
	 * resample->buffer are copied to the beginning of resample->buffer.
	 * The first xoff part of this will be used as history for the next
	 * run, and the second xoff part of this is actually the start of
	 * resampling for the next run.
	 *
	 * And the first run completes, the function returns.
	 *
	 * 
	 * On the next run, the input frame supplied by application is again
	 * copied at 2*xoff position in the resample->buffer, and the 
	 * resample algorithm is again invoked at resample->buffer+xoff 
	 * position. So effectively, the resample algorithm will start its
	 * operation on the last xoff from the previous frame, and gets the
	 * history from the last 2*xoff of the previous frame, and the look-
	 * ahead from the last xoff of current frame.
	 *
	 * So on this run, the buffer layout is:
	 *
	 * run 1
	 *     +------+------+--------------+
	 *     | frm0 | frm0 |  frame1...   |
	 *     +------+------+--------------+
	 *     ^      ^      ^              ^
         *     0    xoff  2*xoff       size+2*xoff 
	 *
	 * As you can see from above diagram, the resampling algorithm is
	 * actually called from the last xoff part of previous frame (frm0).
	 *
	 * And so on the process continues for the next frame, and the next,
	 * and the next, ...
	 *
	 */
	dst_buf = resample->buffer + resample->xoff*2;
	pjmedia_copy_samples(dst_buf, input, resample->frame_size);

	res_Resample(resample->buffer + resample->xoff, output,
		     resample->factor, (pj_uint16_t)resample->frame_size,
		     (char)resample->large_filter, (char)PJ_TRUE);

	dst_buf = resample->buffer;
	src_buf = input + resample->frame_size - resample->xoff*2;
	pjmedia_copy_samples(dst_buf, src_buf, resample->xoff * 2);

    } else {
	res_SrcLinear( input, output, resample->factor, 
		       (pj_uint16_t)resample->frame_size);
    }
}

PJ_DEF(unsigned) pjmedia_resample_get_input_size(pjmedia_resample *resample)
{
    PJ_ASSERT_RETURN(resample != NULL, 0);
    return resample->frame_size;
}

PJ_DEF(void) pjmedia_resample_destroy(pjmedia_resample *resample)
{
    PJ_UNUSED_ARG(resample);
}


#else /* PJMEDIA_HAS_LIBRESAMPLE */

/*
 * This is the configuration when sample rate conversion is disabled.
 */
struct pjmedia_resample
{
	unsigned samples_per_frame;
};

PJ_DEF(pj_status_t) pjmedia_resample_create( pj_pool_t *pool,
					     pj_bool_t high_quality,
					     pj_bool_t large_filter,
					     unsigned channel_count,
					     unsigned rate_in,
					     unsigned rate_out,
					     unsigned samples_per_frame,
					     pjmedia_resample **p_resample) 
{
	pjmedia_resample *resample;
	
	PJ_ASSERT_RETURN(rate_in == rate_out, PJ_EINVALIDOP);

	PJ_UNUSED_ARG(high_quality);
	PJ_UNUSED_ARG(large_filter);
	PJ_UNUSED_ARG(channel_count);
	PJ_UNUSED_ARG(rate_in);
	PJ_UNUSED_ARG(rate_out);
		
	resample = PJ_POOL_ZALLOC_T(pool, pjmedia_resample);
	resample->samples_per_frame = samples_per_frame;
	
	*p_resample = resample;
	
	return PJ_SUCCESS;
}

PJ_DEF(void) pjmedia_resample_run( pjmedia_resample *resample,
				   const pj_int16_t *input,
				   pj_int16_t *output ) 
{
	pjmedia_copy_samples(output, input, resample->samples_per_frame);
}

PJ_DEF(unsigned) pjmedia_resample_get_input_size(pjmedia_resample *resample) 
{
	return resample->samples_per_frame;
}

PJ_DEF(void) pjmedia_resample_destroy(pjmedia_resample *resample) 
{
	PJ_UNUSED_ARG(resample);
}

#endif	/* PJMEDIA_HAS_LIBRESAMPLE */