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Fix mixing of mono -- do 32-bit add and preserve all 17 bits for later dithering

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Mike Brady
2017-05-11 06:48:37 +01:00
parent 1281655b45
commit 3d5d39c841
1 changed files with 29 additions and 24 deletions
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player.c
+29 -24
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@@ -1535,7 +1535,7 @@ static void *player_thread_func(void *arg) {
config.output->play(silence, conn->max_frames_per_packet * conn->output_sample_ratio);
} else {
int enable_dither = 0;
if ((conn->fix_volume != 0x10000) || (conn->input_bit_depth > output_bit_depth))
if ((conn->fix_volume != 0x10000) || (conn->input_bit_depth > output_bit_depth) || (config.playback_mode == ST_mono))
enable_dither = 1;
// here, let's transform the frame of data, if necessary
@@ -1544,6 +1544,7 @@ static void *player_thread_func(void *arg) {
case 16: {
int i, j;
int16_t ls, rs;
int32_t ll, rl;
int16_t *inps = inbuf;
int16_t *outps = tbuf;
int32_t *outpl = (int32_t *)tbuf;
@@ -1552,43 +1553,47 @@ static void *player_thread_func(void *arg) {
rs = *inps++;
// here, do the mode stuff -- mono / reverse stereo / leftonly / rightonly
// also, raise the 16-bit samples to 32 bits.
switch (config.playback_mode) {
case ST_mono: {
int both = ls + rs;
// Note -- this is assuming 16 bit signed.
if (both > INT16_MAX) {
both = INT16_MAX;
} else if (both < INT16_MIN) {
both = INT16_MIN;
}
int16_t sboth = (int16_t)both;
ls = sboth;
rs = sboth;
int32_t both = ls + rs;
both = both<<(16-1); // keep all 17 bits of the sum of the 16bit left and right -- the 17th bit will influence dithering later
ll = both;
rl = both;
} break;
case ST_reverse_stereo: {
int16_t t = ls;
ls = rs;
rs = t;
} break;
ll = rs;
rl = ls;
ll = ll<<16;
rl = rl<<16;
} break;
case ST_left_only:
rs = ls;
break;
rl = ls;
ll = ls;
ll = ll<<16;
rl = rl<<16;
break;
case ST_right_only:
ls = rs;
ll = rs;
rl = rs;
ll = ll<<16;
rl = rl<<16;
break;
case ST_stereo:
break; // nothing extra to do
ll = ls;
rl = rs;
ll = ll<<16;
rl = rl<<16;
break; // nothing extra to do
}
// here, replicate the samples if you're upsampling
for (j = 0; j < conn->output_sample_ratio; j++) {
// raise the 16-bit sample to 32 bits.
int32_t t = ls << 16;
*outpl++ = t;
int32_t u = rs << 16;
*outpl++ = u;
*outpl++ = ll;
*outpl++ = rl;
}
}