ref: 2a38f4826e162c193b00682b7a6a8fe1fddf42e6
dir: /libfaac/joint.c/
/************************* MPEG-2 NBC Audio Decoder **************************
* *
"This software module was originally developed in the course of
development of the MPEG-2 NBC/MPEG-4 Audio standard ISO/IEC 13818-7,
14496-1,2 and 3. This software module is an implementation of a part of one or more
MPEG-2 NBC/MPEG-4 Audio tools as specified by the MPEG-2 NBC/MPEG-4
Audio standard. ISO/IEC gives users of the MPEG-2 NBC/MPEG-4 Audio
standards free license to this software module or modifications thereof for use in
hardware or software products claiming conformance to the MPEG-2 NBC/MPEG-4
Audio standards. Those intending to use this software module in hardware or
software products are advised that this use may infringe existing patents.
The original developer of this software module and his/her company, the subsequent
editors and their companies, and ISO/IEC have no liability for use of this software
module or modifications thereof in an implementation. Copyright is not released for
non MPEG-2 NBC/MPEG-4 Audio conforming products.The original developer
retains full right to use the code for his/her own purpose, assign or donate the
code to a third party and to inhibit third party from using the code for non
MPEG-2 NBC/MPEG-4 Audio conforming products. This copyright notice must
be included in all copies or derivative works."
Copyright(c)1996.
* *
****************************************************************************/
/*
* $Id: joint.c,v 1.7 2001/09/04 18:39:36 menno Exp $
*/
#include "channels.h"
#include "util.h"
void MSEncode(CoderInfo *coderInfo,
ChannelInfo *channelInfo,
double *spectrum[MAX_CHANNELS],
unsigned int numberOfChannels,
unsigned int msenable)
{
unsigned int chanNum;
int sfbNum;
int lineNum;
double sum,diff;
/* Look for channel_pair_elements */
for (chanNum=0;chanNum<numberOfChannels;chanNum++) {
if (channelInfo[chanNum].present) {
if ((channelInfo[chanNum].cpe)&&(channelInfo[chanNum].ch_is_left)) {
int leftChan=chanNum;
int rightChan = channelInfo[chanNum].paired_ch;
channelInfo[leftChan].msInfo.is_present = 0;
channelInfo[rightChan].msInfo.is_present = 0;
/* Perform MS if block_types are the same */
if ((coderInfo[leftChan].block_type==coderInfo[rightChan].block_type)&&(msenable)) {
int numGroups;
int maxSfb;
int g,w,line_offset;
int startWindow,stopWindow;
MSInfo *msInfoL;
MSInfo *msInfoR;
channelInfo[leftChan].common_window = 1; /* Use common window */
channelInfo[leftChan].msInfo.is_present = 1;
channelInfo[rightChan].msInfo.is_present = 1;
numGroups = coderInfo[leftChan].num_window_groups;
maxSfb = coderInfo[leftChan].max_sfb;
w=0;
/* Determine which bands should be enabled */
msInfoL = &(channelInfo[leftChan].msInfo);
msInfoR = &(channelInfo[rightChan].msInfo);
/* Perform sum and differencing on bands in which ms_used flag */
/* has been set. */
if (coderInfo[leftChan].block_type == ONLY_SHORT_WINDOW) {
line_offset=0;
startWindow = 0;
for (g=0;g<numGroups;g++) {
int numWindows = coderInfo[leftChan].window_group_length[g];
stopWindow = startWindow + numWindows;
for (sfbNum=0;sfbNum<maxSfb;sfbNum++) {
/* Enable MS mask */
int use_ms = 1;
for (w=startWindow;w<stopWindow;w++) {
use_ms = min(use_ms, msInfoL->ms_usedS[w][sfbNum]);
}
msInfoL->ms_used[g*maxSfb+sfbNum] = use_ms; /* write this to bitstream */
msInfoR->ms_used[g*maxSfb+sfbNum] = use_ms;
for (w=startWindow;w<stopWindow;w++) {
msInfoL->ms_usedS[w][sfbNum] = use_ms;
msInfoR->ms_usedS[w][sfbNum] = use_ms;
}
for (w=startWindow;w<stopWindow;w++) {
if (msInfoL->ms_usedS[w][sfbNum]) {
for (lineNum = coderInfo[leftChan].sfb_offset[sfbNum];
lineNum < coderInfo[leftChan].sfb_offset[sfbNum+1];
lineNum++)
{
line_offset = w*BLOCK_LEN_SHORT;
sum=spectrum[leftChan][line_offset+lineNum]+spectrum[rightChan][line_offset+lineNum];
diff=spectrum[leftChan][line_offset+lineNum]-spectrum[rightChan][line_offset+lineNum];
spectrum[leftChan][line_offset+lineNum] = 0.5 * sum;
spectrum[rightChan][line_offset+lineNum] = 0.5 * diff;
}
}
}
}
startWindow = stopWindow;
}
} else {
for (sfbNum = 0;sfbNum < maxSfb; sfbNum++) {
msInfoR->ms_used[sfbNum] = msInfoL->ms_used[sfbNum];
/* Enable MS mask */
if (msInfoL->ms_used[sfbNum]) {
for (lineNum = coderInfo[leftChan].sfb_offset[sfbNum];
lineNum < coderInfo[leftChan].sfb_offset[sfbNum+1];
lineNum++)
{
sum=spectrum[leftChan][lineNum]+spectrum[rightChan][lineNum];
diff=spectrum[leftChan][lineNum]-spectrum[rightChan][lineNum];
spectrum[leftChan][lineNum] = 0.5 * sum;
spectrum[rightChan][lineNum] = 0.5 * diff;
}
}
}
}
}
}
}
}
}
void MSReconstruct(CoderInfo *coderInfo,
ChannelInfo *channelInfo,
int numberOfChannels)
{
int chanNum;
int sfbNum;
int lineNum;
double sum,diff;
/* Look for channel_pair_elements */
for (chanNum=0;chanNum<numberOfChannels;chanNum++) {
if (channelInfo[chanNum].present) {
if ((channelInfo[chanNum].cpe)&&(channelInfo[chanNum].ch_is_left)) {
int leftChan=chanNum;
int rightChan=channelInfo[chanNum].paired_ch;
MSInfo *msInfoL;
msInfoL = &(channelInfo[leftChan].msInfo);
if (msInfoL->is_present) {
int numGroups = coderInfo[leftChan].num_window_groups;
int maxSfb = coderInfo[leftChan].max_sfb;
int w,line_offset;
int startWindow;
w=0;
line_offset=0;
startWindow = 0;
if (coderInfo[leftChan].block_type != ONLY_SHORT_WINDOW) {
for (sfbNum = 0;sfbNum < maxSfb; sfbNum++) {
if (msInfoL->ms_used[sfbNum]) {
for (lineNum = coderInfo[leftChan].sfb_offset[sfbNum];
lineNum < coderInfo[leftChan].sfb_offset[sfbNum+1];
lineNum++)
{
sum=coderInfo[leftChan].requantFreq[lineNum];
diff=coderInfo[rightChan].requantFreq[lineNum];
coderInfo[leftChan].requantFreq[lineNum] = (sum+diff);
coderInfo[rightChan].requantFreq[lineNum] = (sum-diff);
}
}
}
}
}
}
}
}
}