Writing hot cue and memory cue points

[laker-93]

Hello and Happy New Year! Many thanks for this awesome project.
I was wondering what the plan is for being able to write both memory cue points and hot cue points to the meta data files?
The readme currently says:

"The files have names like ANLZ0000 and come with the extensions .DAT, .EXT or .2EX. They include waveforms, beat grids (information about the precise time at which each beat occurs), time indices to allow efficient seeking to specific positions inside variable bit-rate audio streams, and lists of memory cues and loop point."

So as it stands, is pyrekordbox able to parse the files were memory cue points are set? What needs to be done in order to write memory and hot cue points? I'd be happy to work on this.

Thanks,

Luke

[dylanljones]

Hey Luke,

Thank you and a happy new year to you too!

Cue points in Rekordbox are a bit confusing. The local cue points are stored in the DjmdCues table of the master.db database, not in the ANLZ files. I am guessing the cue points are written to the exported ANLZ files when preparing the USB drive. I haven't checked the exported ANLZ files though, so far I only looked at the local ANLZ files. In the exported ANLZ files, the cue points should be stored in the PCOB and PCO2 tags. These tags are empty in the local ANLZ files for me.

Accessing the cue points in the database is really straight forward. Using the newest version v0.3.2, the cue points of a DjmdContent can be accessed via a simple relationship:

from pyrekordbox import Rekordbox6Database

db = Rekordbox6Database()
content = db.get_content(ID=<content id>)
for cue in content.Cues:
    print(cue)

I actually just started to work on full cue point support in the database handler, check the cue branch here;) Adding new cue points to the database is simple for most tracks, however I am a little stuck on tracks with variable or average bit rate (ABR/VBR). For this the InMpegFrame and InMpegAbs are required. The latter is the byte offset in the file where the starting frame appears (see djmdcue). Any help on this is more than welcome:)

[laker-93]

Thanks for the detailed response. So presumably this targets rekordbox 6 exclusively for now without rekordbox 5 support? Also is the MBR/ABR only required for supporting cue writes to tracks from streaming services? If so perhaps this could be deferred to a separate issue so that the main feature of writing cues for locally stored tracks can be released.

[dylanljones]

ABR/VBR is a feature of Mp3 files, which consist of MPEG frames. Each frame can have a different bit or sample rate. These values are stored in the frame header, see for example here. I don't really use streaming services, so I don't know how those tracks are represented in the database, but I guess this also applies to streamed tracks.
At least for Mp3 files it would be necessary to read the frame headers and figure out the bit rate for each frame.

[dylanljones]

The MP3 frame headers can now be parse via Ffprobe or a pure Python implementation as fallback, see the cues branch.
Checking for VBR/ABR encoding works as expected, but I still can't reproduce the correct InMpegAbs values.
Until we can figure this out, a NotImplementedError is raised if a VBR/ABR encoded MP3 file is detected.

[laker-93]

Hey Dylan. What's the latest status with the cues branch? Happy to pick this up. For my use case, I don't need streaming track support. Just being able to read/write cue points for normal audio files is good enough for me. Specifically, I'd like to read the cue points from a RB 5 or RB 6 XML, then create a new XML (5 or 6) and write the cue points back in to the new file - thereby preserving the cue information when creating a new XML from an old one. Thanks :)

[Bide-UK]

I've been thinking/looking into this problem on off for longer than I'd like to admit.
After the car crash that is Rekordbox 7 and how they're now essentially charging for this feature... I'm also happy to look at contributing.
I've looked at the commit, if you're able to provide an update on what you've implemented/tried that would be a great place to know where to start. Support VBR/ABR is non trivial but if you can support fixed bitrate tracks to begin wit that would a great place to start.