Add support for internal cue sheets stored in CUESHEET metadata block of FLAC file

[siebenstreich]

It seems that there are two ways how cue sheets are internally stored in FLAC files. The "official" way, which is produced for example by executing

flac --cuesheet=[file.cue] [file.flac]

is to store the cue sheet in a seperate metadata block in the FLAC metadata.
When I execute split2flac on a FLAC file with such an "official" internal cue sheet, I get the message
"No cue sheet"
So I guess that this kind of internal cue sheet is not supported right now.

It would be great if support for those "official" internal cue sheets could be added to split2flac.

The CUESHEET block can be extracted with

metaflac –export-cuesheet-to=[file.cue] [file.flac]

The relevant part in the output of

metaflac --list [file.flac]

on a FLAC file with a cue sheet in a CUESHEET block looks like this, for example:

METADATA block #2
type: 5 (CUESHEET)
is last: false
length: 1236
media catalog number:
lead-in: 88200
is CD: true
number of tracks: 15
track[0]
offset: 0
number: 1
ISRC: BRGI30500001
type: AUDIO
pre-emphasis: false
number of index points: 1
index[0]
offset: 0
number: 1
track[1]
offset: 11625348
number: 2
ISRC: BRGI30500002
type: AUDIO
pre-emphasis: false
number of index points: 1
index[0]
offset: 0
number: 1
[...]
track[14]
offset: 155611848
number: 170 (LEAD-OUT)

Some information on the version numbers on my system:

split2flac -v
split2flac version: 114

shntool 3.0.7
flac 1.2.1
oggenc from vorbis-tools 1.4.0
LAME 64bits version 3.99.5 (http://lame.sf.net)

[diffycat]

@mkimki , it seems that metadata block stores only index information (without title,preformer and other fields). Is it ok or I've missed something?

[diffycat]

Nevermind, I've found explanation: https://xiph.org/flac/faq.html#general__no_cuesheet_tags

[siebenstreich]

Wow, that was really fast. Thank you!!
Yeah, the CUESHEET block is not for ALBUM, ARTIST ect, which probably is the reason for the existence of the second way for storing the cue sheet.

The program flactag stores this information in the following way (part of metaflac --list output):

METADATA block #3
type: 4 (VORBIS_COMMENT)
is last: false
length: 3585
vendor string: reference libFLAC 1.3.0 20130526
comments: 92
comment[0]: ALBUM=4321
comment[1]: ARTIST=Giana Viscardi
comment[2]: ARTISTSORT=Viscardi, Giana
comment[3]: DATE=2005
comment[4]: MUSICBRAINZ_ALBUMARTISTID=fbb2d494-bb5b-4e70-a288-73a87f7ca4e9
comment[5]: MUSICBRAINZ_ALBUMID=bd306992-e25b-44a7-9700-73bf0b02516e
comment[6]: MUSICBRAINZ_ALBUMSTATUS=official
comment[7]: MUSICBRAINZ_ALBUMTYPE=album
comment[8]: TRACKNUMBER[1]=1
comment[9]: ARTIST[1]=Giana Viscardi
comment[10]: ARTISTSORT[1]=Viscardi, Giana
comment[11]: MUSICBRAINZ_ARTISTID[1]=fbb2d494-bb5b-4e70-a288-73a87f7ca4e9
comment[12]: MUSICBRAINZ_TRACKID[1]=2bf0af4f-d425-43b1-9af4-cadefab4e08c
comment[13]: TITLE[1]=4321
comment[14]: TRACKNUMBER[2]=2
comment[15]: ARTIST[2]=Giana Viscardi
comment[16]: ARTISTSORT[2]=Viscardi, Giana
comment[17]: MUSICBRAINZ_ARTISTID[2]=fbb2d494-bb5b-4e70-a288-73a87f7ca4e9
comment[18]: MUSICBRAINZ_TRACKID[2]=4d4cf9bc-a369-4646-8243-8f4c3c311f85
comment[19]: TITLE[2]=Metades
[...]

I don't know if this is a more widespread method to store the metadata. Do you think it is worth to be supported by split2flac?

[diffycat]

@mkimki , that will be more complicated than just sed one-liner. I'll try to add it, but don't know when. Also it will be interesting to add new ability to download information from musicbrainz and write it instead of cue-data.