[mkv] How to obtain `InfoElement::title` (mkv segment title)?

[hasezoey]

[mkv] How to obtain `InfoElement::title` (mkv segment title)?

[pdeljanov]

Hey @dedobbin, @hasezoey,

The title provided in the Info element is like a general title for the segment. Within the segment, more detailed tags may be provided via the Tags element.

I don't really like the idea of overwriting one title with the other, so here are two possible solutions:

1. Since the Info element would come first, if a title is present, create a MetadataRevision and add the title to it. Push the revision to the MetadataLog. Then, add the tags from the Tags element to a new MetadataRevision, and push it to the MetadataLog. In this way, both titles are accessible with a logical order (Info element, then Tags).
2. Use the same MetadataRevision for both the Info and Tags element tags, but use a hardcoded tag name of SEGMENT_TITLE (v.s., the regular TITLE) for the Info element segment title.

I'm leaning towards 2 because it's easier for the end-user, but 1 has some perks too (the end-user doesn't need to look for two different tag names).

[dedobbin]

@pdeljanov Sorry for late response. Holiday happened haha.

Hmm yeah i think solution 1 is the cleanest. Solution 2 was also something i had in mind because it's simpler but feels bit arbitrary to map it to a specific key for Symphonia.

Yeah my vote goes to solution 1.

[dedobbin]

Hey thanks for the report. I do find it a bit odd how ffmpeg approaches the title tag, but regardless

In Symphonia, it seems the title from InfoElement is not properly used, removing #[allow(dead_code)] from https://github.com/pdeljanov/Symphonia/blob/master/symphonia-format-mkv/src/segment.rs#L272 reveals as much.

Even though it seems in the realm of MKV metadata usually only refers to the TagsElement, i would argue this title from the InfoElement could also be considered metadata, so we can store it in the metadata structure.

I think this would automatically prioritize the title of the TagsElement since it shows up later in the file and would probably overwrite the title entry by InfoElement, same behavior as ffmpeg.

Do you think this is a good way to approach it @pdeljanov ?

[hasezoey]

i am personally fine with either way, as long as it is available as a Metadata tag in some way (and not some out-of-the-way function) and is documented what the difference with the normal TITLE would be.

[pdeljanov]

Yeah, it'd be a bespoke tag for MKV. We can document it in the symphonia-format-mkv crate, but it wouldn't be particularly obvious unless one looks there. In this regard, solution 1 is marginally better because we could just use the typical TITLE tag name and assign the a StandardTagKey to it.

@dedobbin, any thoughts?