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separate the actual math for recovering stereo from a signal channel, this is to allow fixpoint implementation

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Originally committed as revision 9698 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Marc Hoffman 2007-07-16 11:25:56 +00:00
parent e2e2e7dd70
commit dc0c20f99b
1 changed files with 25 additions and 5 deletions
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30
libavcodec/cook.c
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@ -741,6 +741,30 @@ static void decouple_info(COOKContext *q, int* decouple_tab){
return;
}
/*
* function decouples a pair of signals from a single signal via multiplication.
*
* @param q pointer to the COOKContext
* @param subband index of the current subband
* @param f1 multiplier for channel 1 extraction
* @param f2 multiplier for channel 2 extraction
* @param decode_buffer input buffer
* @param mlt_buffer1 pointer to left channel mlt coefficients
* @param mlt_buffer2 pointer to right channel mlt coefficients
*/
static void decouple_float (COOKContext *q,
int subband,
float f1, float f2,
float *decode_buffer,
float *mlt_buffer1, float *mlt_buffer2)
{
int j, tmp_idx;
for (j=0 ; j<SUBBAND_SIZE ; j++) {
tmp_idx = ((q->js_subband_start + subband)*SUBBAND_SIZE)+j;
mlt_buffer1[SUBBAND_SIZE*subband + j] = f1 * decode_buffer[tmp_idx];
mlt_buffer2[SUBBAND_SIZE*subband + j] = f2 * decode_buffer[tmp_idx];
}
}
/**
* function for decoding joint stereo data
@ -785,11 +809,7 @@ static void joint_decode(COOKContext *q, float* mlt_buffer1,
cplscale = (float*)cplscales[q->js_vlc_bits-2]; //choose decoupler table
f1 = cplscale[decouple_tab[cpl_tmp]];
f2 = cplscale[idx-1];
for (j=0 ; j<SUBBAND_SIZE ; j++) {
tmp_idx = ((q->js_subband_start + i)*20)+j;
mlt_buffer1[20*i + j] = f1 * decode_buffer[tmp_idx];
mlt_buffer2[20*i + j] = f2 * decode_buffer[tmp_idx];
}
decouple_float (q, i, f1, f2, decode_buffer, mlt_buffer1, mlt_buffer2);
idx = (1 << q->js_vlc_bits) - 1;
}
}