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(svn r17146) -Codechange: improve the sample rate conversion a bit

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rubidium
2009-08-10 17:46:44 +00:00
parent a5364ea13b
commit 362dc78607
2 changed files with 24 additions and 5 deletions
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23
src/mixer.cpp
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@@ -36,6 +36,19 @@ static uint32 _play_rate = 11025;
*/
static const int MAX_VOLUME = 128 * 128;
/**
* Perform the rate conversion between the input and output.
* @param b the buffer to read the data from
* @param frac_pos the position from the begin of the buffer till the next element
* @tparam T the size of the buffer (8 or 16 bits)
* @return the converted value.
*/
template <typename T>
static int RateConversion(T *b, int frac_pos)
{
return ((b[0] * ((1 << 16) - frac_pos)) + (b[1] * frac_pos)) >> 16;
}
static void mix_int16(MixerChannel *sc, int16 *buffer, uint samples)
{
int16 *b;
@@ -64,8 +77,9 @@ static void mix_int16(MixerChannel *sc, int16 *buffer, uint samples)
} while (--samples > 0);
} else {
do {
buffer[0] = Clamp(buffer[0] + (*b * volume_left >> 16), -MAX_VOLUME, MAX_VOLUME);
buffer[1] = Clamp(buffer[1] + (*b * volume_right >> 16), -MAX_VOLUME, MAX_VOLUME);
int data = RateConversion(b, frac_pos);
buffer[0] = Clamp(buffer[0] + (data * volume_left >> 16), -MAX_VOLUME, MAX_VOLUME);
buffer[1] = Clamp(buffer[1] + (data * volume_right >> 16), -MAX_VOLUME, MAX_VOLUME);
buffer += 2;
frac_pos += frac_speed;
b += frac_pos >> 16;
@@ -105,8 +119,9 @@ static void mix_int8_to_int16(MixerChannel *sc, int16 *buffer, uint samples)
} while (--samples > 0);
} else {
do {
buffer[0] = Clamp(buffer[0] + (*b * volume_left >> 8), -MAX_VOLUME, MAX_VOLUME);
buffer[1] = Clamp(buffer[1] + (*b * volume_right >> 8), -MAX_VOLUME, MAX_VOLUME);
int data = RateConversion(b, frac_pos);
buffer[0] = Clamp(buffer[0] + (data * volume_left >> 8), -MAX_VOLUME, MAX_VOLUME);
buffer[1] = Clamp(buffer[1] + (data * volume_right >> 8), -MAX_VOLUME, MAX_VOLUME);
buffer += 2;
frac_pos += frac_speed;
b += frac_pos >> 16;