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oggdec: resample to target frequency

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This commit is contained in:
cinap_lenrek 2012-02-06 03:34:21 +01:00
parent 9d60d8262e
commit 1a450db960
1 changed files with 76 additions and 50 deletions
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126
sys/src/cmd/audio/oggdec/oggdec.c
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@ -26,11 +26,82 @@
#include <math.h>
#include <vorbis/codec.h>
int rate = 44100;
ogg_int16_t convbuffer[4096]; /* take 8k out of the data segment, not the stack */
int convsize=4096;
enum {
Max = 32767,
Min = -32768,
};
extern void _VDBG_dump(void);
typedef unsigned long ulong;
typedef unsigned char uchar;
typedef struct Chan Chan;
struct Chan
{
unsigned long phase;
float last;
};
static uchar*
resample(Chan *c, float *src, uchar *dst, int mono, ulong delta, ulong count)
{
float f, last, val;
ulong phase, pos;
int out;
last = c->last;
phase = c->phase;
pos = phase >> 16;
while(pos < count){
val = src[pos];
if(pos)
last = src[pos-1];
f = (float)(phase&0xFFFF)/0x10000;
out = (last + (val - last) * f) * 32767.f;
/* cliping */
if(out > Max)
out = Max;
else if(out < Min)
out = Min;
*dst++ = out;
*dst++ = out >> 8;
if(mono){
*dst++ = out;
*dst++ = out >> 8;
} else
dst += 2;
phase += delta;
pos = phase >> 16;
}
c->last = val;
if(delta < 0x10000)
c->phase = phase & 0xFFFF;
else
c->phase = phase - (count << 16);
return dst;
}
static void
output(float **pcm, int samples, vorbis_info *vi)
{
static uchar *buf;
static int nbuf;
static Chan c1, c0;
ulong n, delta;
uchar *p;
delta = ((ulong)vi->rate << 16) / rate;
n = 4 * ((ulong)vi->rate + samples * rate) / (ulong)vi->rate;
if(n > nbuf){
nbuf = n;
buf = realloc(buf, nbuf);
}
if(vi->channels == 2)
resample(&c1, pcm[1], buf+2, 0, delta, samples);
p = resample(&c0, pcm[0], buf, vi->channels == 1, delta, samples);
fwrite(buf, p-buf, 1, stdout);
}
int main(){
ogg_sync_state oy; /* sync and verify incoming physical bitstream */
@ -167,8 +238,6 @@ int main(){
fprintf(stderr,"Encoded by: %s\n\n",vc.vendor);
}
convsize=4096/vi.channels;
/* OK, got and parsed all three headers. Initialize the Vorbis
packet->PCM decoder. */
vorbis_synthesis_init(&vd,&vi); /* central decode state */
@ -196,56 +265,13 @@ int main(){
if(result<0){ /* missing or corrupt data at this page position */
/* no reason to complain; already complained above */
}else{
/* we have a packet. Decode it */
float **pcm;
int samples;
if(vorbis_synthesis(&vb,&op)==0) /* test for success! */
vorbis_synthesis_blockin(&vd,&vb);
/*
**pcm is a multichannel float vector. In stereo, for
example, pcm[0] is left, and pcm[1] is right. samples is
the size of each channel. Convert the float values
(-1.<=range<=1.) to whatever PCM format and write it out */
while((samples=vorbis_synthesis_pcmout(&vd,&pcm))>0){
int j;
int clipflag=0;
int bout=(samples<convsize?samples:convsize);
/* convert floats to 16 bit signed ints (host order) and
interleave */
for(i=0;i<vi.channels;i++){
ogg_int16_t *ptr=convbuffer+i;
float *mono=pcm[i];
for(j=0;j<bout;j++){
#if 1
int val=mono[j]*32767.f;
#else /* optional dither */
int val=mono[j]*32767.f+drand48()-0.5f;
#endif
/* might as well guard against clipping */
if(val>32767){
val=32767;
clipflag=1;
}
if(val<-32768){
val=-32768;
clipflag=1;
}
*ptr=val;
ptr+=vi.channels;
}
}
if(clipflag)
fprintf(stderr,"Clipping in frame %ld\n",(long)(vd.sequence));
fwrite(convbuffer,2*vi.channels,bout,stdout);
vorbis_synthesis_read(&vd,bout); /* tell libvorbis how
output(pcm, samples, &vi);
vorbis_synthesis_read(&vd,samples); /* tell libvorbis how
many samples we
actually consumed */
}