/*

Simple DirectMedia Layer

This software is provided 'as-is', without any express or implied

warranty. In no event will the authors be held liable for any damages

arising from the use of this software.

Permission is granted to anyone to use this software for any purpose,

including commercial applications, and to alter it and redistribute it

freely, subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must not

claim that you wrote the original software. If you use this software

in a product, an acknowledgment in the product documentation would be

appreciated but is not required.

2. Altered source versions must be plainly marked as such, and must not be

misrepresented as being the original software.

3. This notice may not be removed or altered from any source distribution.

*/

#include "../SDL_internal.h"

/* Functions for audio drivers to perform runtime conversion of audio format */

#include "SDL_audio.h"

#include "SDL_audio_c.h"

#include "SDL_cpuinfo.h"

#ifdef __SSE3__

#define HAVE_SSE3_INTRINSICS 1

#endif

#if HAVE_SSE3_INTRINSICS

/* Effectively mix right and left channels into a single channel */

static void SDLCALL

SDL_ConvertStereoToMono_SSE3(SDL_AudioCVT * cvt, SDL_AudioFormat format)

{

float *dst = (float *) cvt->buf;

const float *src = dst;

int i = cvt->len_cvt / 8;

LOG_DEBUG_CONVERT("stereo", "mono (using SSE3)");

SDL_assert(format == AUDIO_F32SYS);

/* We can only do this if dst is aligned to 16 bytes; since src is the

same pointer and it moves by 2, it can't be forcibly aligned. */

if ((((size_t) dst) & 15) == 0) {

/* Aligned! Do SSE blocks as long as we have 16 bytes available. */

const __m128 divby2 = _mm_set1_ps(0.5f);

while (i >= 4) { /* 4 * float32 */

_mm_store_ps(dst, _mm_mul_ps(_mm_hadd_ps(_mm_load_ps(src), _mm_load_ps(src+4)), divby2));

i -= 4; src += 8; dst += 4;

}

}

/* Finish off any leftovers with scalar operations. */

while (i) {

*dst = (src[0] + src[1]) * 0.5f;

dst++; i--; src += 2;

}

cvt->len_cvt /= 2;

if (cvt->filters[++cvt->filter_index]) {

cvt->filters[cvt->filter_index] (cvt, format);

}

}

#endif

/* Effectively mix right and left channels into a single channel */

static void SDLCALL

float *dst = (float *) cvt->buf;

const float *src = dst;

int i;

LOG_DEBUG_CONVERT("stereo", "mono");

SDL_assert(format == AUDIO_F32SYS);

for (i = cvt->len_cvt / 8; i; --i, src += 2) {

}

cvt->len_cvt /= 2;

if (cvt->filters[++cvt->filter_index]) {

cvt->filters[cvt->filter_index] (cvt, format);

}

}

float *dst = (float *) cvt->buf;

const float *src = dst;

int i;

const double front_center = (double) src[2];

dst[0] = (float) ((src[0] + front_center + src[4]) / 3.0); /* left */

dst[1] = (float) ((src[1] + front_center + src[5]) / 3.0); /* right */

}

cvt->len_cvt /= 3;

if (cvt->filters[++cvt->filter_index]) {

cvt->filters[cvt->filter_index] (cvt, format);

}

}

float *dst = (float *) cvt->buf;

const float *src = dst;

int i;

/* FIXME: this is a good candidate for SIMD. */

const double front_center = (double) src[2];

dst[0] = (float) ((src[0] + front_center) * 0.5); /* FL */

dst[1] = (float) ((src[1] + front_center) * 0.5); /* FR */

dst[2] = (float) ((src[4] + front_center) * 0.5); /* BL */

dst[3] = (float) ((src[5] + front_center) * 0.5); /* BR */

}

cvt->len_cvt /= 6;

cvt->len_cvt *= 4;

if (cvt->filters[++cvt->filter_index]) {

cvt->filters[cvt->filter_index] (cvt, format);

}

}

/* Duplicate a mono channel to both stereo channels */

static void SDLCALL

const float *src = (const float *) (cvt->buf + cvt->len_cvt);

float *dst = (float *) (cvt->buf + cvt->len_cvt * 2);

int i;

LOG_DEBUG_CONVERT("mono", "stereo");

SDL_assert(format == AUDIO_F32SYS);

for (i = cvt->len_cvt / sizeof (float); i; --i) {

src--;

dst -= 2;

dst[0] = dst[1] = *src;

}

cvt->len_cvt *= 2;

if (cvt->filters[++cvt->filter_index]) {

cvt->filters[cvt->filter_index] (cvt, format);

}

}

/* Duplicate a stereo channel to a pseudo-5.1 stream */

static void SDLCALL

{

int i;

float lf, rf, ce;

const float *src = (const float *) (cvt->buf + cvt->len_cvt);

float *dst = (float *) (cvt->buf + cvt->len_cvt * 3);

LOG_DEBUG_CONVERT("stereo", "5.1");

SDL_assert(format == AUDIO_F32SYS);

for (i = cvt->len_cvt / 8; i; --i) {

dst -= 6;

src -= 2;

lf = src[0];

rf = src[1];

ce = (lf + rf) * 0.5f;

dst[0] = lf + (lf - ce); /* FL */

dst[1] = rf + (rf - ce); /* FR */

dst[2] = ce; /* FC */

dst[3] = ce; /* !!! FIXME: wrong! This is the subwoofer. */

dst[4] = lf; /* BL */

dst[5] = rf; /* BR */

cvt->len_cvt *= 3;

if (cvt->filters[++cvt->filter_index]) {

cvt->filters[cvt->filter_index] (cvt, format);

}

}

/* Duplicate a stereo channel to a pseudo-4.0 stream */

static void SDLCALL

const float *src = (const float *) (cvt->buf + cvt->len_cvt);

float *dst = (float *) (cvt->buf + cvt->len_cvt * 2);

int i;

LOG_DEBUG_CONVERT("stereo", "quad");

SDL_assert(format == AUDIO_F32SYS);

for (i = cvt->len_cvt / 8; i; --i) {

dst -= 4;

src -= 2;

lf = src[0];

rf = src[1];

dst[0] = lf; /* FL */

dst[1] = rf; /* FR */

dst[2] = lf; /* BL */

dst[3] = rf; /* BR */

cvt->len_cvt *= 2;

if (cvt->filters[++cvt->filter_index]) {

cvt->filters[cvt->filter_index] (cvt, format);

}

}

static int

SDL_ResampleAudioSimple(const int chans, const double rate_incr,

float *last_sample, const float *inbuf,

const int inbuflen, float *outbuf, const int outbuflen)

{

const int finalpos = (total * chans) - chans;

const int dest_samples = (int)(((double)total) * rate_incr);

float *dst;

double idx;

int i;

SDL_assert((inbuflen % framelen) == 0);

float *target = (outbuf + chans);

dst = outbuf + (dest_samples * chans);

idx = (double) total;

if (chans == 1) {

const float final_sample = inbuf[finalpos];

float earlier_sample = inbuf[finalpos];

while (dst > target) {

const int pos = ((int) idx) * chans;

const float *src = &inbuf[pos];

SDL_assert(pos >= 0.0);

*(--dst) = (val + earlier_sample) * 0.5f;

earlier_sample = val;

idx -= src_incr;

}

/* do last sample, interpolated against previous run's state. */

*(--dst) = (inbuf[0] + last_sample[0]) * 0.5f;

*last_sample = final_sample;

} else if (chans == 2) {

const float final_sample2 = inbuf[finalpos+1];

const float final_sample1 = inbuf[finalpos];

float earlier_sample2 = inbuf[finalpos];

float earlier_sample1 = inbuf[finalpos-1];

while (dst > target) {

const int pos = ((int) idx) * chans;

const float *src = &inbuf[pos];

const float val2 = *(--src);

const float val1 = *(--src);

SDL_assert(pos >= 0.0);

*(--dst) = (val2 + earlier_sample2) * 0.5f;

*(--dst) = (val1 + earlier_sample1) * 0.5f;

earlier_sample2 = val2;

earlier_sample1 = val1;

idx -= src_incr;

/* do last sample, interpolated against previous run's state. */

*(--dst) = (inbuf[1] + last_sample[1]) * 0.5f;

*(--dst) = (inbuf[0] + last_sample[0]) * 0.5f;

last_sample[1] = final_sample2;

last_sample[0] = final_sample1;

} else {

const float *earlier_sample = &inbuf[finalpos];

float final_sample[8];

SDL_memcpy(final_sample, &inbuf[finalpos], framelen);

while (dst > target) {

const int pos = ((int) idx) * chans;

const float *src = &inbuf[pos];

SDL_assert(pos >= 0.0);

for (i = chans - 1; i >= 0; i--) {

const float val = *(--src);

*(--dst) = (val + earlier_sample[i]) * 0.5f;

}

earlier_sample = src;

idx -= src_incr;

}

/* do last sample, interpolated against previous run's state. */

for (i = chans - 1; i >= 0; i--) {

const float val = inbuf[i];

*(--dst) = (val + last_sample[i]) * 0.5f;

}

SDL_memcpy(last_sample, final_sample, framelen);

}

float *target = (outbuf + (dest_samples * chans));

dst = outbuf;

idx = 0.0;

if (chans == 1) {

float last = *last_sample;

while (dst < target) {

const int pos = ((int) idx) * chans;

const float val = inbuf[pos];

SDL_assert(pos <= finalpos);

*(dst++) = (val + last) * 0.5f;

last = val;

idx += src_incr;

}

*last_sample = last;

} else if (chans == 2) {

float last1 = last_sample[0];

float last2 = last_sample[1];

while (dst < target) {

const int pos = ((int) idx) * chans;

const float val1 = inbuf[pos];

const float val2 = inbuf[pos+1];

SDL_assert(pos <= finalpos);

*(dst++) = (val1 + last1) * 0.5f;

*(dst++) = (val2 + last2) * 0.5f;

last1 = val1;

last2 = val2;

idx += src_incr;

}

last_sample[0] = last1;

last_sample[1] = last2;

} else {

while (dst < target) {

const int pos = ((int) idx) * chans;

const float *src = &inbuf[pos];

SDL_assert(pos <= finalpos);

for (i = 0; i < chans; i++) {

const float val = *(src++);

*(dst++) = (val + last_sample[i]) * 0.5f;

last_sample[i] = val;

}

idx += src_incr;

}

}

}

/* We keep one special-case fast path around for an extremely common audio format. */

static int

SDL_ResampleAudioSimple_si16_c2(const double rate_incr,

Sint16 *last_sample, const Sint16 *inbuf,

const int inbuflen, Sint16 *outbuf, const int outbuflen)

{

const int chans = 2;

const int framelen = 4; /* stereo 16 bit */

const int total = (inbuflen / framelen);

const int finalpos = (total * chans) - chans;

const int dest_samples = (int)(((double)total) * rate_incr);

const double src_incr = 1.0 / rate_incr;

Sint16 *dst;

double idx;

SDL_assert((dest_samples * framelen) <= outbuflen);

SDL_assert((inbuflen % framelen) == 0);

if (rate_incr > 1.0) {

Sint16 *target = (outbuf + chans);

const Sint16 final_right = inbuf[finalpos+1];

const Sint16 final_left = inbuf[finalpos];

Sint16 earlier_right = inbuf[finalpos-1];

Sint16 earlier_left = inbuf[finalpos-2];

dst = outbuf + (dest_samples * chans);

idx = (double) total;

while (dst > target) {

const int pos = ((int) idx) * chans;

const Sint16 *src = &inbuf[pos];

const Sint16 right = *(--src);

const Sint16 left = *(--src);

SDL_assert(pos >= 0.0);

*(--dst) = (((Sint32) right) + ((Sint32) earlier_right)) >> 1;

*(--dst) = (((Sint32) left) + ((Sint32) earlier_left)) >> 1;

earlier_right = right;

earlier_left = left;

idx -= src_incr;

}

/* do last sample, interpolated against previous run's state. */

*(--dst) = (((Sint32) inbuf[1]) + ((Sint32) last_sample[1])) >> 1;

*(--dst) = (((Sint32) inbuf[0]) + ((Sint32) last_sample[0])) >> 1;

last_sample[1] = final_right;

last_sample[0] = final_left;

} else {

Sint16 *target = (outbuf + (dest_samples * chans));

dst = outbuf;

idx = 0.0;

while (dst < target) {

const int pos = ((int) idx) * chans;

const Sint16 *src = &inbuf[pos];

const Sint16 left = *(src++);

const Sint16 right = *(src++);

SDL_assert(pos <= finalpos);

*(dst++) = (((Sint32) left) + ((Sint32) last_sample[0])) >> 1;

*(dst++) = (((Sint32) right) + ((Sint32) last_sample[1])) >> 1;

last_sample[0] = left;

last_sample[1] = right;

idx += src_incr;

}

}

return (int) ((dst - outbuf) * ((int) sizeof (Sint16)));

}

static void SDLCALL

SDL_ResampleCVT_si16_c2(SDL_AudioCVT *cvt, SDL_AudioFormat format)

{

const Sint16 *src = (const Sint16 *) cvt->buf;

const int srclen = cvt->len_cvt;

Sint16 *dst = (Sint16 *) cvt->buf;

const int dstlen = (cvt->len * cvt->len_mult);

Sint16 state[2] = { src[0], src[1] };

SDL_assert(format == AUDIO_S16SYS);

cvt->len_cvt = SDL_ResampleAudioSimple_si16_c2(cvt->rate_incr, state, src, srclen, dst, dstlen);

if (cvt->filters[++cvt->filter_index]) {

cvt->filters[cvt->filter_index](cvt, format);

}

}

int

SDL_ConvertAudio(SDL_AudioCVT * cvt)

{

/* !!! FIXME: (cvt) should be const; stack-copy it here. */

/* !!! FIXME: (actually, we can't...len_cvt needs to be updated. Grr.) */

/* Make sure there's data to convert */

if (cvt->buf == NULL) {

/* Return okay if no conversion is necessary */

cvt->len_cvt = cvt->len;

if (cvt->filters[0] == NULL) {

}

/* Set up the conversion and go! */

cvt->filter_index = 0;

cvt->filters[0] (cvt, cvt->src_format);

}

static void SDLCALL

SDL_Convert_Byteswap(SDL_AudioCVT *cvt, SDL_AudioFormat format)

#if DEBUG_CONVERT

printf("Converting byte order\n");

#endif

switch (SDL_AUDIO_BITSIZE(format)) {

#define CASESWAP(b) \

case b: { \

Uint##b *ptr = (Uint##b *) cvt->buf; \

int i; \

for (i = cvt->len_cvt / sizeof (*ptr); i; --i, ++ptr) { \

*ptr = SDL_Swap##b(*ptr); \

} \

break; \

}

CASESWAP(16);

CASESWAP(32);

CASESWAP(64);

#undef CASESWAP

default: SDL_assert(!"unhandled byteswap datatype!"); break;

}

if (cvt->filters[++cvt->filter_index]) {

/* flip endian flag for data. */

if (format & SDL_AUDIO_MASK_ENDIAN) {

format &= ~SDL_AUDIO_MASK_ENDIAN;

} else {

format |= SDL_AUDIO_MASK_ENDIAN;

}

cvt->filters[cvt->filter_index](cvt, format);

}

}

static int

if ((SDL_AUDIO_ISBIGENDIAN(src_fmt) != 0) == (SDL_BYTEORDER == SDL_LIL_ENDIAN)) {

cvt->filters[cvt->filter_index++] = SDL_Convert_Byteswap;

retval = 1; /* added a converter. */

}

const Uint16 src_bitsize = SDL_AUDIO_BITSIZE(src_fmt);

const Uint16 dst_bitsize = 32;

switch (src_fmt & ~SDL_AUDIO_MASK_ENDIAN) {

case AUDIO_S8: filter = SDL_Convert_S8_to_F32; break;

case AUDIO_U8: filter = SDL_Convert_U8_to_F32; break;

case AUDIO_S16: filter = SDL_Convert_S16_to_F32; break;

case AUDIO_S32: filter = SDL_Convert_S32_to_F32; break;

default: SDL_assert(!"Unexpected audio format!"); break;

}

if (!filter) {

return SDL_SetError("No conversion available for these formats");

}

cvt->filters[cvt->filter_index++] = filter;

if (src_bitsize < dst_bitsize) {

const int mult = (dst_bitsize / src_bitsize);

cvt->len_mult *= mult;

cvt->len_ratio *= mult;

} else if (src_bitsize > dst_bitsize) {

cvt->len_ratio /= (src_bitsize / dst_bitsize);

}

}

}

static int

SDL_BuildAudioTypeCVTFromFloat(SDL_AudioCVT *cvt, const SDL_AudioFormat dst_fmt)

int retval = 0; /* 0 == no conversion necessary. */

if (!SDL_AUDIO_ISFLOAT(dst_fmt)) {

const Uint16 dst_bitsize = SDL_AUDIO_BITSIZE(dst_fmt);

const Uint16 src_bitsize = 32;

SDL_AudioFilter filter = NULL;

switch (dst_fmt & ~SDL_AUDIO_MASK_ENDIAN) {

case AUDIO_S8: filter = SDL_Convert_F32_to_S8; break;

case AUDIO_U8: filter = SDL_Convert_F32_to_U8; break;

case AUDIO_S16: filter = SDL_Convert_F32_to_S16; break;

case AUDIO_S32: filter = SDL_Convert_F32_to_S32; break;

default: SDL_assert(!"Unexpected audio format!"); break;

}

if (!filter) {

return SDL_SetError("No conversion available for these formats");

}

cvt->filters[cvt->filter_index++] = filter;

if (src_bitsize < dst_bitsize) {

const int mult = (dst_bitsize / src_bitsize);

cvt->len_mult *= mult;

cvt->len_ratio *= mult;

} else if (src_bitsize > dst_bitsize) {

cvt->len_ratio /= (src_bitsize / dst_bitsize);

}

retval = 1; /* added a converter. */

}

if ((SDL_AUDIO_ISBIGENDIAN(dst_fmt) != 0) == (SDL_BYTEORDER == SDL_LIL_ENDIAN)) {

cvt->filters[cvt->filter_index++] = SDL_Convert_Byteswap;

retval = 1; /* added a converter. */

}

return retval;

}

static void

SDL_ResampleCVT(SDL_AudioCVT *cvt, const int chans, const SDL_AudioFormat format)

{

const float *src = (const float *) cvt->buf;

const int srclen = cvt->len_cvt;

float *dst = (float *) cvt->buf;

const int dstlen = (cvt->len * cvt->len_mult);

SDL_assert(format == AUDIO_F32SYS);

if (cvt->filters[++cvt->filter_index]) {

cvt->filters[cvt->filter_index](cvt, format);

}

}

/* !!! FIXME: We only have this macro salsa because SDL_AudioCVT doesn't

!!! FIXME: store channel info, so we have to have function entry

!!! FIXME: points for each supported channel count and multiple

!!! FIXME: vs arbitrary. When we rev the ABI, clean this up. */

#define RESAMPLER_FUNCS(chans) \

static void SDLCALL \

SDL_ResampleCVT_c##chans(SDL_AudioCVT *cvt, SDL_AudioFormat format) { \

SDL_ResampleCVT(cvt, chans, format); \

}

RESAMPLER_FUNCS(1)

RESAMPLER_FUNCS(2)

RESAMPLER_FUNCS(4)

RESAMPLER_FUNCS(6)

RESAMPLER_FUNCS(8)

#undef RESAMPLER_FUNCS

switch (dst_channels) {

case 1: return SDL_ResampleCVT_c1;

case 2: return SDL_ResampleCVT_c2;

case 4: return SDL_ResampleCVT_c4;

case 6: return SDL_ResampleCVT_c6;

case 8: return SDL_ResampleCVT_c8;

default: break;

}

}

static int

SDL_BuildAudioResampleCVT(SDL_AudioCVT * cvt, const int dst_channels,

const int src_rate, const int dst_rate)

{

SDL_AudioFilter filter;

if (src_rate == dst_rate) {

return 0; /* no conversion necessary. */

}

if (filter == NULL) {

return SDL_SetError("No conversion available for these rates");

}

/* Update (cvt) with filter details... */

cvt->filters[cvt->filter_index++] = filter;

if (src_rate < dst_rate) {

const double mult = ((double) dst_rate) / ((double) src_rate);

cvt->len_mult *= (int) SDL_ceil(mult);

cvt->len_ratio *= mult;

} else {

cvt->len_ratio /= ((double) src_rate) / ((double) dst_rate);

}

}

/* Creates a set of audio filters to convert from one format to another.

Returns -1 if the format conversion is not supported, 0 if there's

no conversion needed, or 1 if the audio filter is set up.

*/

int

SDL_BuildAudioCVT(SDL_AudioCVT * cvt,

SDL_AudioFormat src_fmt, Uint8 src_channels, int src_rate,

SDL_AudioFormat dst_fmt, Uint8 dst_channels, int dst_rate)

{

/* Sanity check target pointer */

if (cvt == NULL) {

return SDL_InvalidParamError("cvt");

}

/* Make sure we zero out the audio conversion before error checking */

SDL_zerop(cvt);

/* there are no unsigned types over 16 bits, so catch this up front. */

if ((SDL_AUDIO_BITSIZE(src_fmt) > 16) && (!SDL_AUDIO_ISSIGNED(src_fmt))) {

return SDL_SetError("Invalid source format");

}

if ((SDL_AUDIO_BITSIZE(dst_fmt) > 16) && (!SDL_AUDIO_ISSIGNED(dst_fmt))) {

return SDL_SetError("Invalid destination format");

}

/* prevent possible divisions by zero, etc. */

if ((src_channels == 0) || (dst_channels == 0)) {

return SDL_SetError("Source or destination channels is zero");

}

if ((src_rate == 0) || (dst_rate == 0)) {

return SDL_SetError("Source or destination rate is zero");

}

printf("Build format %04x->%04x, channels %u->%u, rate %d->%d\n",

src_fmt, dst_fmt, src_channels, dst_channels, src_rate, dst_rate);

#endif

/* Start off with no conversion necessary */

cvt->src_format = src_fmt;

cvt->dst_format = dst_fmt;

cvt->needed = 0;

cvt->filter_index = 0;

cvt->filters[0] = NULL;

cvt->len_mult = 1;

cvt->len_ratio = 1.0;

cvt->rate_incr = ((double) dst_rate) / ((double) src_rate);

/* SDL now favors float32 as its preferred internal format, and considers

everything else to be a degenerate case that we might have to make

multiple passes over the data to convert to and from float32 as

necessary. That being said, we keep one special case around for

efficiency: stereo data in Sint16 format, in the native byte order,

that only needs resampling. This is likely to be the most popular

legacy format, that apps, hardware and the OS are likely to be able

to process directly, so we handle this one case directly without

unnecessary conversions. This means that apps on embedded devices

without floating point hardware should consider aiming for this

format as well. */

if ((src_channels == 2) && (dst_channels == 2) && (src_fmt == AUDIO_S16SYS) && (dst_fmt == AUDIO_S16SYS) && (src_rate != dst_rate)) {

cvt->needed = 1;

cvt->filters[cvt->filter_index++] = SDL_ResampleCVT_si16_c2;

if (src_rate < dst_rate) {

const double mult = ((double) dst_rate) / ((double) src_rate);

cvt->len_mult *= (int) SDL_ceil(mult);

cvt->len_ratio *= mult;

} else {

cvt->len_ratio /= ((double) src_rate) / ((double) dst_rate);

}

return 1;

}

/* Type conversion goes like this now:

- byteswap to CPU native format first if necessary.

- convert to native Float32 if necessary.

- resample and change channel count if necessary.

- convert back to native format.

- byteswap back to foreign format if necessary.

The expectation is we can process data faster in float32

(possibly with SIMD), and making several passes over the same

biggest performance hit in modern times. Previously we had

(script-generated) custom converters for every data type and

it was a bloat on SDL compile times and final library size. */

/* see if we can skip float conversion entirely. */

if (src_rate == dst_rate && src_channels == dst_channels) {

if (src_fmt == dst_fmt) {

return 0;

}

/* just a byteswap needed? */

if ((src_fmt & ~SDL_AUDIO_MASK_ENDIAN) == (dst_fmt & ~SDL_AUDIO_MASK_ENDIAN)) {

cvt->filters[cvt->filter_index++] = SDL_Convert_Byteswap;

cvt->needed = 1;

return 1;

}

}

return -1; /* shouldn't happen, but just in case... */

}

/* Channel conversion */

if (src_channels != dst_channels) {

if ((src_channels == 1) && (dst_channels > 1)) {

cvt->len_mult *= 2;

src_channels = 2;

cvt->len_ratio *= 2;

}

if ((src_channels == 2) && (dst_channels == 6)) {

src_channels = 6;

cvt->len_mult *= 3;

cvt->len_ratio *= 3;

}

if ((src_channels == 2) && (dst_channels == 4)) {

src_channels = 4;

cvt->len_mult *= 2;

cvt->len_ratio *= 2;

}

while ((src_channels * 2) <= dst_channels) {

cvt->len_mult *= 2;

src_channels *= 2;

cvt->len_ratio *= 2;

}

if ((src_channels == 6) && (dst_channels <= 2)) {

src_channels = 2;

cvt->len_ratio /= 3;

}

if ((src_channels == 6) && (dst_channels == 4)) {