How can i extract DVD Chapter titles using libdvdread or libdvdnav?

[Earthnuker]

Hello everyone,

I am currently working on a cross-platform DVD Ripper built on top of libdvdread and libdvdnav and i have noticed that MakeMKV can extract "proper" chapter names from certain DVDs (Zentrix Volume 1 Disc 1 in this case) which are apparently stored in VIDEO_TS.IFO (see attached screenshot) but have not found a way to get them using VLC's libdvdread or libdvdnav (and opening the ISO in VLC also does not show the chapter names).



If anyone has any pointer towards where i could find more info on how and where they are stored i would greatly appreciate that.

Best regards,

Earthnuker

[Earthnuker]

After some messing around with ifoEdit i figured it out:

- open VIDEO_TS.IFO (DVDOpenFile(handle, 0, dvd_read_domain_t::DVD_READ_INFO_FILE))
- seek to offset 0xd4
- read a 32-bit big endian unsigned integer (U32BE)
- seek to that offset in blocks (offset*2048 in bytes)
- skip 0xc bytes (company ID)
- read number of language units as U32BE
- read end_byte offset as U32BE
- for each language unit
   - read 1 U16BE (language code)
   - skip 6 bytes (unknown)
- for each language unit
   - skip 4 + 2 + 2 + 9 * 20 + 16 = 204 bytes
   - read num_entries as U16BE 
   - skip 2 bytes
   - check if num_entries is even (if not throw error?)
   - divide num_entries by 2 (reserved)
   - for each entry:
      - read entry_type U32LE
      - skip 4 byte (unknown)
- read tab (0x9) separated strings until you've reached position offset+end_byte

entry types seem to be:
- 0x1 for disc
- 0x2 for feature title
- 0x4 for chapter title
- 0x46 for ??? (contians "Spruce0200MenuGPRM03ITag b68" in my case)

[Emulgator]

You may go from there:
http://mpucoder.com/DVD/ifo.html

[Earthnuker]

Originally Posted by Emulgator

You may go from there:
http://mpucoder.com/DVD/ifo.html

I did stumble upon that site during my research, sadly it doesn't contain any info on how the data in the VMG_TXTDT_MG is laid out, so it's not too useful, and all the other data i need is already extracted by libdvdread and libdvdnav

[hubblec4]

Hi Earthnuker

That is very interesting and I have never found such info while I wrote my own IFO parser.
Could you imagine to share with me the DVD you had mentioned? Or if the entire DVD is to much, the IFO files would be also helpful.

[Earthnuker]

Originally Posted by hubblec4

Hi Earthnuker

That is very interesting and I have never found such info while I wrote my own IFO parser.
Could you imagine to share with me the DVD you had mentioned? Or if the entire DVD is to much, the IFO files would be also helpful.

I have uploaded the VIDEO_TS.IFO file to https://s31.0w0.wtf/s/wHC9dDgs4JrcNwA (Nextcloud instance hosted by a friend) i do have an ISO of the DVD but it's over 5GB so uploading that somewhere might take a while, i had thought it was available on archive.org, but i must have been mixing it up with something else

[hubblec4]

Many thanks for this VIDEO_TS.IFO file.
I hope it is enough to figure out everything for parsing the chapter names.

[Emulgator]

DVD Architect Pro allows for named chapters, once I find time I can make some test projects.

[Emulgator]

Well, DVD-A 7.0 does not seem to render the chapter names from its timeline window into the VIDEO_TS.IFO
I can input up to 39 characters per Chapter, even Unicode symbols (musical notes) were accepted, except the first chapter 1, this can not be named.
After rendering and opening with MakeMKV only standard names are assigned : Chapter 01, Chapter 02...
DVDLabPro2: One cannot enter chapter names there anyway. MakeMKV shows the same.

[Emulgator]

Just downloaded Earthnuker's VIDEO_TS.IFO.
BTW, good find, Earthnuker. Did not go through all steps but the concatenation of all strings at the end
indeed tells that applying the calculated offsets one should be able to parse following your procedure in post #2.