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mp3dec: fix volume for mp3dec

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the libmad samples need to be scaled properly. the
previous assumption was that it is 32 bits, but it
really is MAD_F_FRACTBITS + sign bit and rest used
for overflow.

thanks eekee!
This commit is contained in:
cinap_lenrek 2013-11-06 22:18:36 +01:00
parent 7b36a7e1a9
commit a60001871e
1 changed files with 8 additions and 1 deletions
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9
sys/src/cmd/audio/mp3dec/main.c
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@ -46,7 +46,7 @@ output(void *, struct mad_header const* header, struct mad_pcm *pcm)
rate = pcm->samplerate;
chans = pcm->channels;
snprint(fmt, sizeof(fmt), "s32r%dc%d", rate, chans);
snprint(fmt, sizeof(fmt), "s%dr%dc%d", MAD_F_FRACBITS+1, rate, chans);
if(ifd >= 0){
close(ifd);
@ -82,6 +82,13 @@ output(void *, struct mad_header const* header, struct mad_pcm *pcm)
p = buf + j*4;
for(i=0; i < pcm->length; i++){
v = *s++;
/* clipping */
if(v >= MAD_F_ONE)
v = MAD_F_ONE-1;
else if(v < -MAD_F_ONE)
v = -MAD_F_ONE;
p[0] = v, v>>=8;
p[1] = v, v>>=8;
p[2] = v, v>>=8;