Mystery Blu-ray audio tracks

[Nermal]

I have the Blu-ray of "Akira" and something weird's happening. The back of the case lists four audio tracks:

1. Japanese 5.1 TrueHD
2. Japanese 5.1 Dolby Digital
3. Japanese 2.0 PCM
4. English 5.1 TrueHD

Those tracks show up on my real Blu-ray player, and also in VLC. However, both IINA and MKVToolNix report six tracks:

1. Japanese 5.1 TrueHD
2. Japanese 2.0 Dolby Digital
3. Japanese 2.0 PCM
4. English 5.1 TrueHD
5. English 5.1 Dolby Digital
6. Japanese 5.1 Dolby Digital

Does anyone know what's going on here? Why do two extra tracks appear when I use different software?

 

[Erehy Dobon]

It's hard to say without listening to the individual audio tracks.

I own some Blu-rays have feature spoken commentary over the main audio tracks. Naturally they aren't separated out on the case box as additional tracks. Perhaps it's how the playback software's author decided to identify the raw tracks.

If you have a Dolby Digital 5.1 track and another version with the director's commentary, is that really two different audio formats? Most people would say no.

I've had to wrangle with the subtitle situation similarly. I own Japanese language Blu-rays that have A.) plain English subtitles but also B.) English subtitles with notations for hearing impaired viewers. Subtitles like [music playing] or [leaves rustling].

On the box art, these are never identified as different subtitle options. In certain software they show up as different subtitle options.

When I do a Handbrake rip from those Blu-rays I have to do practice runs on individual chapters lest I transcode an entire Blu-ray movie with subtitles that I don't want.

 

[Nermal]

They're all 'normal' tracks, not commentary. In any case commentary tracks would still normally show up on the real player and in VLC.

 

[Ritsuka]

TrueHD tracks contains an embedded AC-3 track for players that can't playback TrueHD. VLC lets you select it, some other players might not.

 

[Juicy Box]

I see stuff like this almost daily on both Blu-rays and sometimes DVDs when adding my collection to my Plex library.

It is usually different channel options that are not accessible via the setup options on the disk, and I have even seen hidden commentary tracks that are not advertise, nor accessible otherwise.

 

[priitv8]

This is typical of TrueHD tracks and I believe the reasoning behind it is ffmpeg. Ffmpeg chronically lists THD tracks with embedded AC3 “core” as 2 separate tracks.

 

[Nermal]

This is typical of TrueHD tracks and I believe the reasoning behind it is ffmpeg. Ffmpeg chronically lists THD tracks with embedded AC3 “core” as 2 separate tracks.

That would explain it! I didn't realise that TrueHD had an internal AC3 track but Google is corroborating your story. Thanks!

 

[priitv8]

I didn't realise that TrueHD had an internal AC3 track but Google is corroborating your story.

As I have understood it, THD spec does not mandate it to have a AC3 "core" (in contrast to how DTS-HD builds in layers). The issue here is, that a Blu-Ray spec makes AC3 a mandatory codec and THD is optional codec. So this specific setup appears on BD discs and for the reason of being backwardly compatible with BD specification.

 

[Nermal]

That would further explain why I'd never run into this with HD DVD discs, where TrueHD was common, and mandatory.

 

[priitv8]

That would further explain why I'd never run into this with HD DVD discs, where TrueHD was common, and mandatory.

You are right! There MLP/THD are mandatory.
Blu-Ray spec has created 2 such "workarounds" by now:
1) the TrueHD track with mandatory AC3 compatibility and
2) the Dolby Vision dual-videostream setup with mandatory HDR10 compatibility