eac3to Exploiting Seamless Branching

[BDgeek]

One thing to note, for branched THD tracks, DGDemux approach is different than MLP (even though Rocky*, the developer for DG helped on the MPL project). There's a discussion about it on the "DGDemux development" thread at DG forum around page 73 forward.

So exclusively for branched THD tracks, I like to stick to MLP, while for everything else, I go with DG (video, subtitles, DTS, AC-3 and PCM tracks).

*he's credited on the MLP develper's site.

[Chewtobacca]

Eac3to can demux either the .thd or the ac3 core, but if you output as .thd+ac3, it reencodes the ac3 part from the lossless track, which is slow, and IMO, not ideal.

Oh, for branching discs only! I'm with you now. Sorry; the discussion has wandered a bit, and I thought that you meant that there was a generic problem with the core being re-encoded for all thd+ac3 -track extractions. Yeah, the fact that it's slow is annoying.

[schorman]

Ok, I was able to test DGDemux, and at least for the Star Wars UHD's that I tested, the output was identical to MLP and CloneBD. Judging by the forum posts mentioned by BDgeek, that might not always be true, I guess.

[BDgeek]

Great news schorman!

Thamks a lot for reporting back!

[schorman]

Great news schorman!

Thamks a lot for reporting back!

I did some further testing and can restate that the .thd output by DGdemux exactly matches the .thd output from MLP for brached discs. However, DGdemux does not seem to correctly handle the ac3 core. I've verified a few missing and repeated ac3 frames after re-ripping the 2020 Star Wars UHDs.

It seems like eac3to is still the best way to extract a correctly processed version of the ac3 core from the TrueHD track.

[Chewtobacca]

It's probably worth sharing your findings on the support forum (rationalqm). The author's pretty good at responding to feedback.

And it's good news that MLP handles branched discs with thd properly, so that there's a free option available.

[BDgeek]

Great, thanks a lot for you findings schorman!

As Chewtobacca said, it would be good to share this input on the forum. It was based on my input that Rocky identified and corrected and problem with PCM ripping.

[schorman]

I can do that, I'm just swamped at the moment.

[alleycat]

Sorry to hijack this thread, but just to confirm the official way then that blu rays use seamless branching is to cut the video into segments, version 1 uses A, B, D, F, G and version 2 uses A, B, C, E, F etc? Never really looked into it before but I have an upcoming project where I might use it myself and this is what I was thinking of doing, multiple videos and two playlists. Thanks

[Chewtobacca]

^ That's essentially correct, although there's an audio "frame" of overlap on each side of the join. People often report difficulty creating branching discs, outside of using high-end solutions such as Scenarist. It might be theoretically possible to encode the files in such a way as to ensure seamless playback via a playlist, but you'll have to experiment. I've thought about doing this but have never had cause to try it, so please post your findings. It will be fascinating to see if a poor man's seamless branching can be achieved, and if so, how programs such as eac3to process the results.