Hydrogenaudio Forums > FLAC & seekable Option

mepistop

Apr 27 2004, 02:50

Flac 1.10 (Windows) default encoding with seekable option is default.
Is that "Seekable" option important?

What if I use "--no-seektable" option when I encode?

What's the difference of seektable?

Do I need to keep all of those seektable information in flac file?

Here is my "Metaflac" list information with defalut option:

CODE

METADATA block #0
type: 0 (STREAMINFO)
is last: false
length: 34
minumum blocksize: 4608 samples
maximum blocksize: 4608 samples
minimum framesize: 14 bytes
maximum framesize: 16843 bytes
sample_rate: 44100 Hz
channels: 2
bits-per-sample: 16
total samples: 11378976
MD5 signature: dab1753b29e6593a8f9e81fb44457706
METADATA block #1
type: 3 (SEEKTABLE)
is last: false
length: 450
seek points: 25
point 0: sample_number=0, stream_offset=0, frame_samples=0
point 1: sample_number=451584, stream_offset=0, frame_samples=714360
point 2: sample_number=907776, stream_offset=0, frame_samples=1612600
point 3: sample_number=1363968, stream_offset=0, frame_samples=2599810
point 4: sample_number=1820160, stream_offset=0, frame_samples=3602831
point 5: sample_number=2271744, stream_offset=0, frame_samples=4637984
point 6: sample_number=2727936, stream_offset=0, frame_samples=5730410
point 7: sample_number=3184128, stream_offset=0, frame_samples=6860382
point 8: sample_number=3640320, stream_offset=0, frame_samples=8084635
point 9: sample_number=4091904, stream_offset=0, frame_samples=9334580
point 10: sample_number=4548096, stream_offset=0, frame_samples=10568646
point 11: sample_number=5004288, stream_offset=0, frame_samples=11687999
point 12: sample_number=5460480, stream_offset=0, frame_samples=12859853
point 13: sample_number=5916672, stream_offset=0, frame_samples=14020297
point 14: sample_number=6368256, stream_offset=0, frame_samples=15271218
point 15: sample_number=6824448, stream_offset=0, frame_samples=16554157
point 16: sample_number=7280640, stream_offset=0, frame_samples=17827069
point 17: sample_number=7736832, stream_offset=0, frame_samples=19132661
point 18: sample_number=8188416, stream_offset=0, frame_samples=20354452
point 19: sample_number=8644608, stream_offset=0, frame_samples=21691621
point 20: sample_number=9100800, stream_offset=0, frame_samples=23034895
point 21: sample_number=9556992, stream_offset=0, frame_samples=24402525
point 22: sample_number=10013184, stream_offset=0, frame_samples=25762667
point 23: sample_number=10464768, stream_offset=0, frame_samples=27060899
point 24: sample_number=10920960, stream_offset=0, frame_samples=28062391
METADATA block #2
type: 4 (VORBIS_COMMENT)
is last: false
length: 40
vendor string: reference libFLAC 1.1.0 20030126
comments: 0
METADATA block #3
type: 1 (PADDING)
is last: true
length: 4096

Here is my "Metaflac" list information with option "--no-seektable":

CODE

METADATA block #0
type: 0 (STREAMINFO)
is last: false
length: 34
minumum blocksize: 4608 samples
maximum blocksize: 4608 samples
minimum framesize: 14 bytes
maximum framesize: 11438 bytes
sample_rate: 44100 Hz
channels: 2
bits-per-sample: 16
total samples: 14641200
MD5 signature: 5249ded10e65b404b1306432e34ee974
METADATA block #1
type: 4 (VORBIS_COMMENT)
is last: false
length: 177
vendor string: reference libFLAC 1.1.0 20030126
comments: 6
comment[0]: ALBUM=Let's Get Lost
comment[1]: ARTIST=Chet Baker
comment[2]: GENRE=Jazz
comment[3]: DATE=1989
comment[4]: TRACKNUMBER=1
comment[5]: TITLE=Moon & Sand (Motivo di Raggio di Luna)
METADATA block #2
type: 1 (PADDING)
is last: true
length: 3959

pest

Apr 27 2004, 02:58

if you do not add a seektable to your flac, seeking will be very slow, for example
in foobar. You simply save some bytes. If you never play your flacs or
use them as a backup you could avoid the seektable, but i think it's not recommended...

pest

rtilghman

Apr 28 2004, 16:09

As stated, Seeking will be slow without a Seektable. In addition you won't be able to seek on devices that use a decoder that doesn't add reference seekpoints on the fly when the file is decoded. So while programs like Winamp will still allow seeking, other hardware and software may not.

For example, the Rio Karma is a portable player that plays FLAC files. The reference decoder used is incapable of adding reference seekpoints, as I understand it by design since creating seekpoints would require the disk spin up constantly, resulting in a big battery hit, etc.

Basically for a couple of k just add the seekpoints, theres nothing but negatives to not having a seektable.

-rt

jcoalson

Apr 28 2004, 16:31

adding reference seekpoints on the fly is not a requirement for seeking in FLAC files that have no seektable. even on the Karma it should be possible to seek without a seek table, though it may be slow.

the time it takes to seek without a seektable is a function of the length. the reference decoder's seek algorithm in this case is not as good as a binary search but the next release will have a true binary search.

Josh