[RESOLVED] Demuxed Dolby True HD has no core AC3 track

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squallmx
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[RESOLVED] Demuxed Dolby True HD has no core AC3 track

Post by squallmx » Mon Nov 18, 2019 9:28 am

I'm trying the demux function, works great for seamless branching titles, but when demuxing Dolby THD tracks, the output file lacks the needed core AC3 track for proper Blu-ray compatibility (the core AC3 track is put on a separate file) so TSMuxerGUI fails to recognise said THD file.

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Rocky
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Re: Demuxed Dolby True HD has no core AC3 track

Post by Rocky » Mon Nov 18, 2019 2:00 pm

Not sure what to tell you if some third-party app can't open a pure THD file. mkvtoolnix has no problem with it. It plays in MPC-HC etc.

gonca
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Re: Demuxed Dolby True HD has no core AC3 track

Post by gonca » Mon Nov 18, 2019 4:23 pm

If I may interject,
I may be wrong but THD tracks have no core, an AC3 track is interleaved with it for backward compability, which is why MKVToolNix separates the two.
Also, TSMuxer has not been updated in a very long time.
DTSHD/MA are the ones with a core
Last edited by gonca on Mon Nov 18, 2019 5:35 pm, edited 2 times in total.

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Rocky
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Re: Demuxed Dolby True HD has no core AC3 track

Post by Rocky » Mon Nov 18, 2019 5:13 pm

All correct. Thank you, gonca.

squallmx
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Re: Demuxed Dolby True HD has no core AC3 track

Post by squallmx » Mon Nov 18, 2019 5:23 pm

Rocky wrote:
Mon Nov 18, 2019 2:00 pm
Not sure what to tell you if some third-party app can't open a pure THD file. mkvtoolnix has no problem with it. It plays in MPC-HC etc.
The Blu-ray spec requires for a TrueHD track to have an interleaved AC3 track for backward compatibility (@gonca has a point :agree: , is not a core track, just a compatibility track), so the current THD output file is useless for those wanting to create a BD-25 / BD-50 backups, it would be nice to have an option for a proper THD+AC3 interleaved file, back in the day eac3to was able to create such files, but now it fails on new UHD releases.

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Rocky
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Re: Demuxed Dolby True HD has no core AC3 track

Post by Rocky » Mon Nov 18, 2019 5:30 pm

Please give the relevant paragraph of the bluray spec. I don't doubt you, I just want to see it. I don't rule out adding an option to keep thd+ac3.

squallmx
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Re: Demuxed Dolby True HD has no core AC3 track

Post by squallmx » Mon Nov 18, 2019 7:03 pm

Rocky wrote:
Mon Nov 18, 2019 5:30 pm
Please give the relevant paragraph of the Blu-ray spec. I don't doubt you, I just want to see it. I don't rule out adding an option to keep thd+ac3.
I too poor to have access to the official spec, but is something referenced constantly at that forum by reputable users, for example this post by madashi (creator of eac3to) showthread.php?p=1415246#post1415246
There are 2 different TrueHD streams:

(1) TrueHD+AC3. This is a mixed format. There are both (alternating) TrueHD and AC3 frames in the stream.

(2) TrueHD. This stream only contains TrueHD frames and no AC3 frames.

All Blu-Ray TrueHD streams are (1). All HD DVD TrueHD streams are (2). eac3to can convert between both stream types. Converting from (1) to (2) is very easy: The AC3 frames are simply removed. Converting from (2) to (1) is more difficult: The TrueHD stream must be decoded and reencoded to AC3 and then the AC3 frames must be injected into the TrueHD stream in a specific way.

When muxing to MKV, the AC3 frames are usually removed, so MKV TrueHD streams are usually type (2).

There's no special metadata which tells anyone how to convert TrueHD to AC3, AFAIK.
Since Dolby TrueHD is an optional codec, a companion Dolby Digital bitstream must accompany the Dolby TrueHD bitstream on Blu-ray discs. Blu-ray Disc players consider this combination of two audio bitstreams as a single logical audio track, and a Blu-ray Disc player will automatically select the Dolby Digital or Dolby TrueHD bitstream depending on its decoding and/or bitstreaming capabilities.

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Rocky
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Re: Demuxed Dolby True HD has no core AC3 track

Post by Rocky » Tue Nov 19, 2019 8:37 am

OK, thank you, I have put it on the to-do list.

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Bullwinkle
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Re: Demuxed Dolby True HD has no core AC3 track

Post by Bullwinkle » Wed Dec 04, 2019 10:42 pm

DGDecNV and DGDemux both now allow you to retain THD+AC3 so let's stomp out this thread. See ya!

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