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Fix decoding of multichannel flac, refactor sample buffer handling and decorrelation (taken from ffmpeg sources) and add some flac details to the manual. Solves FS#12371.

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@31207 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Andree Buschmann 2011-12-10 22:28:16 +00:00
parent 09722dd28d
commit a6653a9bb6
4 changed files with 42 additions and 70 deletions
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80
apps/codecs/libffmpegFLAC/decoder.c
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@ -381,17 +381,13 @@ static inline int decode_subframe(FLACContext *s, int channel, int32_t* decoded)
}
static int decode_frame(FLACContext *s,
int32_t* decoded0,
int32_t* decoded1,
void (*yield)(void)) ICODE_ATTR_FLAC;
static int decode_frame(FLACContext *s,
int32_t* decoded0,
int32_t* decoded1,
void (*yield)(void))
{
int blocksize_code, sample_rate_code, sample_size_code, assignment, crc8;
int decorrelation, bps, blocksize, samplerate;
int res;
int res, ch;
blocksize_code = get_bits(&s->gb, 4);
@ -477,16 +473,10 @@ static int decode_frame(FLACContext *s,
s->bps = bps;
s->decorrelation= decorrelation;
yield();
/* subframes */
if ((res=decode_subframe(s, 0, decoded0)) < 0)
return res-100;
yield();
if (s->channels==2) {
if ((res=decode_subframe(s, 1, decoded1)) < 0)
return res-200;
for (ch=0; ch<s->channels; ++ch) {
yield();
if ((res=decode_subframe(s, ch, s->decoded[ch])) < 0)
return res-100;
}
yield();
@ -499,8 +489,6 @@ static int decode_frame(FLACContext *s,
}
int flac_decode_frame(FLACContext *s,
int32_t* decoded0,
int32_t* decoded1,
uint8_t *buf, int buf_size,
void (*yield)(void))
{
@ -516,68 +504,36 @@ int flac_decode_frame(FLACContext *s,
return -41;
}
if ((framesize=decode_frame(s,decoded0,decoded1,yield)) < 0){
if ((framesize=decode_frame(s,yield)) < 0){
s->bitstream_size=0;
s->bitstream_index=0;
return framesize;
}
yield();
#define DECORRELATE(left, right)\
for (i = 0; i < s->blocksize; i++) {\
int a = s->decoded[0][i];\
int b = s->decoded[1][i];\
s->decoded[0][i] = (left) << scale;\
s->decoded[1][i] = (right) << scale;\
}\
scale=FLAC_OUTPUT_DEPTH-s->bps;
switch(s->decorrelation)
{
case INDEPENDENT:
if (s->channels==1) {;
for (i = 0; i < s->blocksize; i++)
{
decoded0[i] = decoded0[i] << scale;
}
} else {
for (i = 0; i < s->blocksize; i++)
{
decoded0[i] = decoded0[i] << scale;
decoded1[i] = decoded1[i] << scale;
}
}
DECORRELATE(a, b) /* Always decorrelate exactly the two supported channels. */
break;
case LEFT_SIDE:
//assert(s->channels == 2);
for (i = 0; i < s->blocksize; i++)
{
decoded1[i] = (decoded0[i] - decoded1[i]) << scale;
decoded0[i] = decoded0[i] << scale;
}
DECORRELATE(a, a-b)
break;
case RIGHT_SIDE:
//assert(s->channels == 2);
for (i = 0; i < s->blocksize; i++)
{
decoded0[i] = (decoded0[i] + decoded1[i]) << scale;
decoded1[i] = decoded1[i] << scale;
}
DECORRELATE(a+b, a)
break;
case MID_SIDE:
//assert(s->channels == 2);
for (i = 0; i < s->blocksize; i++)
{
int mid, side;
mid = decoded0[i];
side = decoded1[i];
#if 1 //needs to be checked but IMHO it should be binary identical
mid -= side>>1;
decoded0[i] = (mid + side) << scale;
decoded1[i] = mid << scale;
#else
mid <<= 1;
if (side & 1)
mid++;
decoded0[i] = ((mid + side) >> 1) << scale;
decoded1[i] = ((mid - side) >> 1) << scale;
#endif
}
DECORRELATE( (a-=b>>1) + b, a)
break;
}