Duplicate Audio Tracks

[Rojma]

Recently I noticed that when I was ripping my Blu-Rays that most of my rips will have two duplicate audio tracks of the same type. For example, I will have two DD Surround 5.1 English tracks. After some research it appears that one of the tracks is a base or core for a higher quality track like TrueHD Surround 7.1 English while the second is a stand-alone track. In the MakeMKV screen the first track will show as a "child" audio track under the higher quality audio track. Are both of these tracks basically the same and duplicate? Can I get rid of one of them or are there differences between the two? Do I need to make sure I keep the first one for the higher quality track to work? My ultimate goal is to have the most audio tracks available for compatibility, but to also discard duplicate tracks that I don't need.

[Woodstock]

Not duplicates, but yes, the AC3 track is a "child" of the TrueHD.

The way most "lossless" encoded tracks work is that there is a "lossy core", and additional information to replace the bits lost in the lossy encode. But not all players can separate the core from the full track, which is why MakeMKV offers the option to pull the core out as its own track.

If your playback environment understands how this works, then you don't need the separate lossy core.

[Rojma]

Thanks for the response. Out of curiosity I extracted the two different DD Surround 5.1 English tracks (using MKVToolNix) from on of my movies and found they only differed in size by 2K for a file that was 460MB. That tells me that the tracks are essentially the same. If I keep the "core" file as part of the MKV and drop the second file, do I lose anything? Wouldn't any client that can't play the higher quality file just drop down to the core file? When would the second file ever be used?

FYI, I am primarily playing these files with Plex and a variety of clients. My clients vary from Nvidia Shield, Amazon Fire devices, iPads, Android phones, and Windows PCs. Nvidia Shield plays pretty much anything you throw at it but I have had problems playing certain higher quality audio streams from the Amazon Fire devices (which is why I ended up buying an Nvidia Shield). Maybe I will do a test where I strip the second DD Surround 5.1 English track from a movie and see how the Amazon Fire devices handle it (e.g. will it show the "core" DD Surround 5.1 English track as a separate track even though I have stripped the second DD Surround 5.1 English track?)

[Woodstock]

The core is what you would have gotten before the marketing hype of "lossless high-definition audio" hit the market. Truth be told (i.e., not marketing talk), the commercial audio encoders are pretty darn good, and, if you don't have a high-end home theater system to play them back, you would be hard pressed to tell the difference between the lossy core and the lossless "full track".

Mainly the differences will show up in the under-20Hz and over-15KHz audio. This is an area where people in the 18-34 demographic believe that have good hearing, and the 35-55 demographic remember thinking they could hear well.

[Rojma]

Sorry the track I was looking to eliminate was the second "duplicate" DD Surround 5.1 English track, not the higher quality TrueHD Surround 7.1 English audio track. Since the second DD Surround 5.1 English track seems to be almost identical to the "core" audio track, I was looking to eliminate this second track. I guess my question is would that cause any problems? If a player needs the DD Surround 5.1 English track could it use the "core" track and not need the second duplicate DD Surround 5.1 English track?