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/*
* Simple mp3 player. Derived from libmad's example minimad.c.
*/
#include <u.h>
#include <libc.h>
#include "mad.h"
/* Current input file */
vlong offset;
int rate = 44100;
int debug = 0;
static enum mad_flow
input(void *, struct mad_stream *stream)
{
int fd, n, m;
static uchar buf[32768];
n = stream->bufend - stream->next_frame;
memmove(buf, stream->next_frame, n);
m = read(0, buf+n, sizeof buf-n);
offset += m;
if(m < 0)
sysfatal("reading input: %r");
if(m == 0)
return MAD_FLOW_STOP;
n += m;
mad_stream_buffer(stream, buf, n);
return MAD_FLOW_CONTINUE;
}
typedef struct Chan Chan;
struct Chan
{
ulong phase;
mad_fixed_t last;
mad_fixed_t rand;
};
#define PRNG(x) (((x)*0x19660dL + 0x3c6ef35fL) & 0xffffffffL)
enum
{
FracBits = MAD_F_FRACBITS,
OutBits = 16,
ScaleBits = FracBits + 1 - OutBits,
LowMask = (1<<ScaleBits) - 1,
Min = -MAD_F_ONE,
Max = MAD_F_ONE - 1,
};
static uchar*
resample(Chan *c, mad_fixed_t *src, uchar *dst, int mono, ulong delta, ulong count)
{
mad_fixed_t last, val, out, rand;
ulong phase, pos;
vlong v;
rand = c->rand;
last = c->last;
phase = c->phase;
pos = phase >> 16;
while(pos < count){
val = src[pos];
if(pos)
last = src[pos-1];
/* interpolate */
v = val;
v -= last;
v *= (phase & 0xFFFF);
out = last + (v >> 16);
/* dithering */
out += (rand & LowMask) - LowMask/2;
rand = PRNG(rand);
/* cliping */
if(out > Max)
out = Max;
else if(out < Min)
out = Min;
out >>= ScaleBits;
*dst++ = out;
*dst++ = out >> 8;
if(mono){
*dst++ = out;
*dst++ = out >> 8;
} else
dst += 2;
phase += delta;
pos = phase >> 16;
}
c->rand = rand;
c->last = val;
if(delta < 0x10000)
c->phase = phase & 0xFFFF;
else
c->phase = phase - (count << 16);
return dst;
}
static enum mad_flow
output(void *, struct mad_header const* header, struct mad_pcm *pcm)
{
static uchar *buf;
static int nbuf;
static Chan c1, c0;
ulong n, delta;
uchar *p;
delta = (pcm->samplerate << 16) / rate;
n = 4 * (pcm->samplerate + pcm->length * rate) / pcm->samplerate;
if(n > nbuf){
nbuf = n;
buf = realloc(buf, nbuf);
}
if(pcm->channels == 2)
resample(&c1, pcm->samples[1], buf+2, 0, delta, pcm->length);
p = resample(&c0, pcm->samples[0], buf, pcm->channels == 1, delta, pcm->length);
write(1, buf, p-buf);
return MAD_FLOW_CONTINUE;
}
static enum mad_flow
error(void *, struct mad_stream *stream, struct mad_frame *frame)
{
if(stream->error == MAD_ERROR_LOSTSYNC){
uchar *p;
ulong n;
p = stream->this_frame;
if(memcmp(p, "TAG", 3)==0){
mad_stream_skip(stream, 128);
return MAD_FLOW_CONTINUE;
}
if(memcmp(p, "ID3", 3)==0){
if(((p[6] | p[7] | p[8] | p[9]) & 0x80) == 0){
n = p[9] | p[8]<<7 | p[7]<<14 | p[6]<<21;
mad_stream_skip(stream, n+10);
return MAD_FLOW_CONTINUE;
}
}
}
if(debug)
fprint(2, "#%lld: %s\n",
offset-(stream->bufend-stream->next_frame),
mad_stream_errorstr(stream));
return MAD_FLOW_CONTINUE;
}
void
usage(void)
{
fprint(2, "usage: %s [ -d ]\n", argv0);
exits("usage");
}
void
main(int argc, char **argv)
{
struct mad_decoder decoder;
ARGBEGIN{
case 'd':
debug++;
break;
default:
usage();
}ARGEND
mad_decoder_init(&decoder, nil, input, nil, nil, output, error, nil);
mad_decoder_run(&decoder, MAD_DECODER_MODE_SYNC);
mad_decoder_finish(&decoder);
exits(0);
}
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