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Corrected front:surround levels

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git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@3374 b3059339-0415-0410-9bf9-f77b7e298cf2
This commit is contained in:
steve 2001-12-07 22:36:33 +00:00
parent 0f864df68d
commit e237409b46
1 changed files with 13 additions and 2 deletions
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15
libao2/pl_surround.c
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@ -155,9 +155,20 @@ static int play(){
out = pl_surround.databuf; in = (int16_t *)ao_plugin_data.data;
for (i=0; i<samples; i++) {
// About the .707 here and the /2 for surround:
// Surround encoding does the following:
// Lt=L+.707*C+.707*S, Rt=R+.707*C-.707*S
// So S needs to be extracted as:
// .707*(L-R)
// But L-R could still be as much as 32767-(-32768), way off scale
// for signed 16 bits, so to avoid running out of bits, whilst still
// keeping levels in balance, we scale L and R down by 3dB (*.707),
// and scale the surround down by 6dB (.707*.707=.5)
// front left and right
out[0] = in[0];
out[1] = in[1];
out[0] = in[0]*.707;
out[1] = in[1]*.707;
// surround - from 15msec ago
out[2] = pl_surround.delaybuf[pl_surround.delaybuf_ptr];
out[3] = -out[2];