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Optimize A-Law and Mu-Law compressors

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This commit is contained in:
f4exb 2019-02-19 23:27:00 +01:00
parent 1823a78509
commit 9d3d4674d7
2 changed files with 6 additions and 6 deletions
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10
sdrbase/audio/audiocompressor.cpp
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@ -86,15 +86,15 @@ void AudioCompressor::fillLUT2()
void AudioCompressor::fillALaw() void AudioCompressor::fillALaw()
{ {
for (int i=-32768; i<32768; i++) { for (int i=-16384; i<16384; i++) {
m_lut[i+32768] = ALaw_Encode(i); m_lut[i+16384] = ALaw_Encode(2*i);
} }
} }
void AudioCompressor::fillULaw() void AudioCompressor::fillULaw()
{ {
for (int i=-32768; i<32768; i++) { for (int i=-16384; i<16384; i++) {
m_lut[i+32768] = MuLaw_Encode(i); m_lut[i+16384] = MuLaw_Encode(2*i);
} }
} }
@ -107,7 +107,7 @@ int16_t AudioCompressor::compress(int16_t sample)
int8_t AudioCompressor::compress8(int16_t sample) int8_t AudioCompressor::compress8(int16_t sample)
{ {
return m_lut[sample + 32768]; return m_lut[sample/2 + 16384];
} }
/* http://dystopiancode.blogspot.com/2012/02/pcm-law-and-u-law-companding-algorithms.html /* http://dystopiancode.blogspot.com/2012/02/pcm-law-and-u-law-companding-algorithms.html

2
sdrbase/audio/audiocompressor.h
View File

@ -37,7 +37,7 @@ private:
int8_t ALaw_Encode(int16_t number); int8_t ALaw_Encode(int16_t number);
int8_t MuLaw_Encode(int16_t number); int8_t MuLaw_Encode(int16_t number);
int16_t m_lut[65536]; int16_t m_lut[32768];
static const uint16_t ALAW_MAX; static const uint16_t ALAW_MAX;
static const uint16_t MULAW_MAX; static const uint16_t MULAW_MAX;
static const uint16_t MULAW_BIAS; static const uint16_t MULAW_BIAS;