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Initial seeking support. This only seeks to the nearest point (before the target sample) in the seektable. NOTE: not all FLAC files have seektables - some front-ends have the skill to create FLAC files without them. You can add seek points every 10 seconds to a FLAC file with the command: metaflac --add-seekpoint=10s file.flac

Browse source 
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@7680 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Dave Chapman 2005-10-29 01:39:07 +00:00
parent d452d26885
commit dff9352430
1 changed files with 106 additions and 10 deletions
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116
apps/codecs/flac.c
View file

@ -33,14 +33,59 @@ struct codec_api* ci;
int32_t decoded0[MAX_BLOCKSIZE] IBSS_ATTR;
int32_t decoded1[MAX_BLOCKSIZE] IBSS_ATTR;
#define MAX_SUPPORTED_SEEKTABLE_SIZE 5000
/* Notes about seeking:
The full seek table consists of:
uint64_t sample (only 36 bits are used)
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.
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.
With the default settings, a typical 4 minute track will contain
24 seek points.
Taking the extreme case of a Rockbox supported file to be a 2GB (compressed)
16-bit/44.1KHz mono stream with a likely uncompressed size of 4GB:
Total duration is: 48694 seconds (about 810 minutes - 13.5 hours)
Total number of seek points: 4869
Therefore we limit the number of seek points to 5000. This is a
very extreme case, and requires 5000*8=40000 bytes of storage.
If we come across a FLAC file with more than this number of seekpoints, we
just use the first 5000.
*/
struct FLACseekpoints {
uint32_t sample;
uint32_t offset;
};
struct FLACseekpoints seekpoints[MAX_SUPPORTED_SEEKTABLE_SIZE];
int nseekpoints;
static bool flac_init(FLACContext* fc)
{
unsigned char buf[255];
bool found_streaminfo=false;
uint32_t seekpoint_hi,seekpoint_lo;
uint32_t offset_hi,offset_lo;
int endofmetadata=0;
int blocklength;
int n;
uint32_t* p;
ci->memset(fc,0,sizeof(FLACContext));
nseekpoints=0;
if (ci->read_filebuf(buf, 4) < 4)
{
@ -92,7 +137,28 @@ static bool flac_init(FLACContext* fc)
found_streaminfo=true;
} else if ((buf[0] & 0x7f) == 3) { /* 3 is the SEEKTABLE block */
ci->advance_buffer(blocklength);
while ((nseekpoints < MAX_SUPPORTED_SEEKTABLE_SIZE) &&
(blocklength >= 18)) {
n=ci->read_filebuf(buf,18);
if (n < 18) return false;
blocklength-=n;
p=(uint32_t*)buf;
seekpoint_hi=betoh32(*(p++));
seekpoint_lo=betoh32(*(p++));
offset_hi=betoh32(*(p++));
offset_lo=betoh32(*(p++));
if ((seekpoint_hi == 0) && (seekpoint_lo != 0xffffffff) &&
(offset_hi == 0)) {
seekpoints[nseekpoints].sample=seekpoint_lo;
seekpoints[nseekpoints].offset=offset_lo;
nseekpoints++;
}
}
/* Skip any unread seekpoints */
if (blocklength > 0)
ci->advance_buffer(blocklength);
} else {
/* Skip to next metadata block */
ci->advance_buffer(blocklength);
@ -107,6 +173,40 @@ static bool flac_init(FLACContext* fc)
}
}
/* A very simple seek implementation - seek to the seekpoint before
the target sample.
This needs to be improved to seek with greater accuracy
*/
bool flac_seek(FLACContext* fc, uint32_t newsample) {
uint32_t offset;
int i;
if (nseekpoints==0) {
offset=0;
} else {
i=nseekpoints-1;
while ((i > 0) && (seekpoints[i].sample > newsample)) {
i--;
}
if ((i==0) && (seekpoints[i].sample > newsample)) {
offset=0;
} else {
offset=seekpoints[i].offset;
}
}
offset+=fc->metadatalength;
if ((off_t)offset < ci->filesize) {
ci->seek_buffer(offset);
return true;
} else {
return false;
}
}
/* this is the codec entry point */
enum codec_status codec_start(struct codec_api* api)
{
@ -163,15 +263,11 @@ enum codec_status codec_start(struct codec_api* api)
/* Deal with any pending seek requests */
if (ci->seek_time) {
/* We only support seeking to start of track at the moment */
if (ci->seek_time==1) {
if (ci->seek_buffer(fc.metadatalength)) {
/* Refill the input buffer */
bytesleft=ci->read_filebuf(buf,sizeof(buf));
ci->set_elapsed(0);
}
}
ci->seek_time = 0;
if (flac_seek(&fc,(ci->seek_time/20) * (ci->id3->frequency/50))) {
/* Refill the input buffer */
bytesleft=ci->read_filebuf(buf,sizeof(buf));
}
ci->seek_time = 0;
}
if((res=flac_decode_frame(&fc,decoded0,decoded1,buf,