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Sample-accurate seeking for FLAC

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@11474 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Adam Boot 2006-11-08 22:00:45 +00:00
parent 0a220b6da6
commit c1916afa41
3 changed files with 241 additions and 49 deletions
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285
apps/codecs/flac.c
View file

@ -46,9 +46,8 @@ int32_t decoded1[MAX_BLOCKSIZE] IBSS_ATTR;
uint64_t offset
uint32_t blocksize
We don't store the blocksize (of the target frame) and we also
limit the sample and offset values to 32-bits - Rockbox doesn't support
files bigger than 2GB on FAT32 filesystems.
We also limit the sample and offset values to 32-bits - Rockbox doesn't
support files bigger than 2GB on FAT32 filesystems.
The reference FLAC encoder produces a seek table with points every
10 seconds, but this can be overridden by the user when encoding a file.
@ -72,17 +71,22 @@ int32_t decoded1[MAX_BLOCKSIZE] IBSS_ATTR;
struct FLACseekpoints {
uint32_t sample;
uint32_t offset;
uint16_t blocksize;
};
struct FLACseekpoints seekpoints[MAX_SUPPORTED_SEEKTABLE_SIZE];
int nseekpoints;
static int8_t *bit_buffer;
static size_t buff_size;
static bool flac_init(FLACContext* fc, int first_frame_offset)
{
unsigned char buf[255];
bool found_streaminfo=false;
uint32_t seekpoint_hi,seekpoint_lo;
uint32_t offset_hi,offset_lo;
uint16_t blocksize;
int endofmetadata=0;
int blocklength;
int n;
@ -90,6 +94,8 @@ static bool flac_init(FLACContext* fc, int first_frame_offset)
ci->memset(fc,0,sizeof(FLACContext));
nseekpoints=0;
fc->sample_skip = 0;
/* Skip any foreign tags at start of file */
ci->seek_buffer(first_frame_offset);
@ -158,14 +164,14 @@ static bool flac_init(FLACContext* fc, int first_frame_offset)
offset_lo=(buf[12] << 24) | (buf[13] << 16) |
(buf[14] << 8) | buf[15];
/* The final two bytes contain the number of samples in the
target frame - but we don't care about that. */
blocksize=(buf[16] << 8) | buf[17];
/* Only store seekpoints where the high 32 bits are zero */
if ((seekpoint_hi == 0) && (seekpoint_lo != 0xffffffff) &&
(offset_hi == 0)) {
seekpoints[nseekpoints].sample=seekpoint_lo;
seekpoints[nseekpoints].offset=offset_lo;
seekpoints[nseekpoints].blocksize=blocksize;
nseekpoints++;
}
}
@ -186,57 +192,234 @@ static bool flac_init(FLACContext* fc, int first_frame_offset)
}
}
/* A very simple seek implementation - seek to the seekpoint before
the target sample.
/* Synchronize to next frame in stream - adapted from libFLAC 1.1.3b2 */
bool frame_sync(FLACContext* fc) {
unsigned int x = 0;
bool cached = false;
This needs to be improved to seek with greater accuracy
*/
bool flac_seek(FLACContext* fc, uint32_t newsample) {
uint32_t offset;
/* Make sure we're byte aligned. */
align_get_bits(&fc->gb);
if (nseekpoints==0) {
/* No seekpoints = no seeking */
return false;
} else {
int i=nseekpoints-1;
while ((i > 0) && (seekpoints[i].sample > newsample)) {
i--;
}
while(1) {
if(fc->gb.size_in_bits - get_bits_count(&fc->gb) < 8) {
/* Error, end of bitstream, a valid stream should never reach here
* since the buffer should contain at least one frame header.
*/
return false;
}
if ((i==0) && (seekpoints[i].sample > newsample)) {
offset=0;
} else {
offset=seekpoints[i].offset;
}
}
if(cached)
cached = false;
else
x = get_bits(&fc->gb, 8);
return ci->seek_buffer(offset+fc->metadatalength);
if(x == 0xff) { /* MAGIC NUMBER for first 8 frame sync bits. */
x = get_bits(&fc->gb, 8);
/* We have to check if we just read two 0xff's in a row; the second
* may actually be the beginning of the sync code.
*/
if(x == 0xff) { /* MAGIC NUMBER for first 8 frame sync bits. */
cached = true;
}
else if(x >> 2 == 0x3e) { /* MAGIC NUMBER for last 6 sync bits. */
/* Succesfully synced. */
break;
}
}
}
/* Advance and init bit buffer to the new frame. */
ci->advance_buffer((get_bits_count(&fc->gb)-16)>>3); /* consumed bytes */
bit_buffer = ci->request_buffer(&buff_size, MAX_FRAMESIZE);
init_get_bits(&fc->gb, bit_buffer, buff_size*8);
/* Decode the frame to verify the frame crc and
* fill fc with its metadata.
*/
if(flac_decode_frame(fc, decoded0, decoded1,
bit_buffer, buff_size, ci->yield) < 0) {
return false;
}
return true;
}
/* A very simple seek implementation - seek to the seekpoint before
the target offset.
/* Seek to sample - adapted from libFLAC 1.1.3b2+ */
bool flac_seek(FLACContext* fc, uint32_t target_sample) {
off_t orig_pos = ci->curpos;
off_t pos = -1;
unsigned long lower_bound, upper_bound;
unsigned long lower_bound_sample, upper_bound_sample;
int i;
unsigned approx_bytes_per_frame;
uint32_t this_frame_sample = fc->samplenumber;
unsigned this_block_size = fc->blocksize;
bool needs_seek = true, first_seek = true;
This needs to be improved to seek with greater accuracy
*/
/* We are just guessing here. */
if(fc->max_framesize > 0)
approx_bytes_per_frame = (fc->max_framesize + fc->min_framesize)/2 + 1;
/* Check if it's a known fixed-blocksize stream. */
else if(fc->min_blocksize == fc->max_blocksize && fc->min_blocksize > 0)
approx_bytes_per_frame = fc->min_blocksize*fc->channels*fc->bps/8 + 64;
else
approx_bytes_per_frame = 4608 * fc->channels * fc->bps/8 + 64;
/* Set an upper and lower bound on where in the stream we will search. */
lower_bound = fc->metadatalength;
lower_bound_sample = 0;
upper_bound = fc->filesize;
upper_bound_sample = fc->totalsamples>0 ? fc->totalsamples : target_sample;
/* Refine the bounds if we have a seektable with suitable points. */
if(nseekpoints > 0) {
/* Find the closest seek point <= target_sample, if it exists. */
for(i = nseekpoints-1; i >= 0; i--) {
if(seekpoints[i].sample <= target_sample)
break;
}
if(i >= 0) { /* i.e. we found a suitable seek point... */
lower_bound = fc->metadatalength + seekpoints[i].offset;
lower_bound_sample = seekpoints[i].sample;
}
/* Find the closest seek point > target_sample, if it exists. */
for(i = 0; i < nseekpoints; i++) {
if(seekpoints[i].sample > target_sample)
break;
}
if(i < nseekpoints) { /* i.e. we found a suitable seek point... */
upper_bound = fc->metadatalength + seekpoints[i].offset;
upper_bound_sample = seekpoints[i].sample;
}
}
while(1) {
/* Check if bounds are still ok. */
if(lower_bound_sample >= upper_bound_sample ||
lower_bound > upper_bound) {
return false;
}
/* Calculate new seek position */
if(needs_seek) {
pos = (off_t)(lower_bound +
(((target_sample - lower_bound_sample) *
(int64_t)(upper_bound - lower_bound)) /
(upper_bound_sample - lower_bound_sample)) -
approx_bytes_per_frame);
if(pos >= (off_t)upper_bound)
pos = (off_t)upper_bound-1;
if(pos < (off_t)lower_bound)
pos = (off_t)lower_bound;
}
if(!ci->seek_buffer(pos))
return false;
bit_buffer = ci->request_buffer(&buff_size, MAX_FRAMESIZE);
init_get_bits(&fc->gb, bit_buffer, buff_size*8);
/* Now we need to get a frame. It is possible for our seek
* to land in the middle of audio data that looks exactly like
* a frame header from a future version of an encoder. When
* that happens, frame_sync() will return false.
* But there is a remote possibility that it is properly
* synced at such a "future-codec frame", so to make sure,
* we wait to see several "unparseable" errors in a row before
* bailing out.
*/
{
unsigned unparseable_count;
bool got_a_frame = false;
for(unparseable_count = 0; !got_a_frame
&& unparseable_count < 10; unparseable_count++) {
if(frame_sync(fc))
got_a_frame = true;
}
if(!got_a_frame) {
ci->seek_buffer(orig_pos);
return false;
}
}
this_frame_sample = fc->samplenumber;
this_block_size = fc->blocksize;
if(target_sample >= this_frame_sample
&& target_sample < this_frame_sample+this_block_size) {
/* Found the frame containing the target sample. */
fc->sample_skip = target_sample - this_frame_sample;
break;
}
if(this_frame_sample + this_block_size >= upper_bound_sample &&
!first_seek) {
if(pos == (off_t)lower_bound || !needs_seek) {
ci->seek_buffer(orig_pos);
return false;
}
/* Our last move backwards wasn't big enough, try again. */
approx_bytes_per_frame *= 2;
continue;
}
/* Allow one seek over upper bound,
* required for streams with unknown total samples.
*/
first_seek = false;
/* Make sure we are not seeking in a corrupted stream */
if(this_frame_sample < lower_bound_sample) {
ci->seek_buffer(orig_pos);
return false;
}
approx_bytes_per_frame = this_block_size*fc->channels*fc->bps/8 + 64;
/* We need to narrow the search. */
if(target_sample < this_frame_sample) {
upper_bound_sample = this_frame_sample + this_block_size;
upper_bound = ci->curpos;
}
else { /* Target is beyond this frame. */
/* We are close, continue in decoding next frames. */
if(target_sample < this_frame_sample + 4*this_block_size) {
pos = ci->curpos + fc->framesize;
needs_seek = false;
}
lower_bound_sample = this_frame_sample + this_block_size;
lower_bound = ci->curpos + fc->framesize;
}
}
return true;
}
/* Seek to file offset */
bool flac_seek_offset(FLACContext* fc, uint32_t offset) {
if (nseekpoints==0) {
/* No seekpoints = no seeking */
return false;
} else {
offset-=fc->metadatalength;
int i=nseekpoints-1;
while ((i > 0) && (seekpoints[i].offset > offset)) {
i--;
}
unsigned unparseable_count;
bool got_a_frame = false;
if ((i==0) && (seekpoints[i].offset > offset)) {
offset=0;
} else {
offset=seekpoints[i].offset;
}
}
if(!ci->seek_buffer(offset))
return false;
return ci->seek_buffer(offset+fc->metadatalength);
bit_buffer = ci->request_buffer(&buff_size, MAX_FRAMESIZE);
init_get_bits(&fc->gb, bit_buffer, buff_size*8);
for(unparseable_count = 0; !got_a_frame
&& unparseable_count < 10; unparseable_count++) {
if(frame_sync(fc))
got_a_frame = true;
}
if(!got_a_frame) {
ci->seek_buffer(fc->metadatalength);
return false;
}
return true;
}
/* this is the codec entry point */
@ -306,7 +489,8 @@ enum codec_status codec_start(struct codec_api* api)
/* Deal with any pending seek requests */
if (ci->seek_time) {
if (flac_seek(&fc,((ci->seek_time-1)/20)*(ci->id3->frequency/50))) {
if (flac_seek(&fc,(uint32_t)(((uint64_t)(ci->seek_time-1)
*ci->id3->frequency)/1000))) {
/* Refill the input buffer */
buf = ci->request_buffer(&bytesleft, MAX_FRAMESIZE);
}
@ -323,10 +507,13 @@ enum codec_status codec_start(struct codec_api* api)
frame++;
ci->yield();
while(!ci->pcmbuf_insert_split((char*)decoded0,(char*)decoded1,
fc.blocksize*4)) {
while(!ci->pcmbuf_insert_split((char*)&decoded0[fc.sample_skip],
(char*)&decoded1[fc.sample_skip],
(fc.blocksize-fc.sample_skip)*4)) {
ci->yield();
}
fc.sample_skip = 0;
/* Update the elapsed-time indicator */
samplesdone=fc.samplenumber+fc.blocksize;

2
apps/codecs/libffmpegFLAC/decoder.c
View file

@ -584,5 +584,7 @@ int flac_decode_frame(FLACContext *s,
break;
}
s->framesize = (get_bits_count(&s->gb)+7)>>3;
return 0;
}

3
apps/codecs/libffmpegFLAC/decoder.h
View file

@ -35,6 +35,9 @@ typedef struct FLACContext {
int bitstream_size;
int bitstream_index;
int sample_skip;
int framesize;
} FLACContext;
int flac_decode_frame(FLACContext *s,