diff options
| -rw-r--r-- | src/pcm_utils.c | 37 |
1 files changed, 25 insertions, 12 deletions
diff --git a/src/pcm_utils.c b/src/pcm_utils.c index 3f9f61969..87df0f026 100644 --- a/src/pcm_utils.c +++ b/src/pcm_utils.c @@ -286,33 +286,46 @@ void pcm_add(char * buffer1, char * buffer2, size_t bufferSize1, mpd_fixed_t temp; int samples1 = bufferSize1 >> 2; int samples2 = bufferSize2 >> 2; - int iScale1 = vol1 >> 2; - int iScale2 = vol2 >> 2; - int shift = 8; + int shift = 10; if(format->bits!=32 || format->fracBits==0 ) { ERROR("Only 32 bit mpd_fixed_t samples are supported in" " pcm_add!\n"); exit(EXIT_FAILURE); } + + /* take care of zero volume cases */ + if(vol2<=0) { + return; + } + if(vol1<=0) { + if(bufferSize1>bufferSize2) { + memcpy(buffer1, buffer2, bufferSize2); + memset(buffer1+bufferSize2, 0, bufferSize1-bufferSize2); + } + else { + memcpy(buffer1, buffer2, bufferSize1); + } + return; + } - /* lower iScale to minimize audio resolution loss */ - /* as long as it can be done without loss */ - while(!(iScale1 & 1) && !(iScale2 & 1) && shift) { - iScale1 >>= 1; - iScale2 >>= 1; + /* lower multiplicator to minimize audio resolution loss */ + while((vol1>31 || !(vol1 & 1)) && (vol2>31 || !(vol2 & 1)) && shift) { + vol1 >>= 1; + vol2 >>= 1; shift--; } - + /* scale and add samples */ /* no check for overflow needed - we trust our headroom is enough */ - while(samples1 && samples2) { - temp = (*buffer32_1 >> shift) * iScale1 + - (*buffer32_2 >> shift) * iScale2; + while(samples1-- && samples2--) { + temp = (*buffer32_1 >> shift) * vol1 + + (*buffer32_2 >> shift) * vol2; *buffer32_1 = temp; buffer32_1++; buffer32_2++; } + /* take care of case where buffer2 > buffer1 */ if(samples2) memcpy(buffer32_1,buffer32_2,samples2<<2); return; |