How many audio tracks?

General questions or discussion about HandBrake, Video and/or audio transcoding, trends etc.
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Blatherscribe
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Joined: Wed Jul 03, 2019 9:13 am

How many audio tracks?

Post by Blatherscribe » Wed Jul 03, 2019 9:18 am

I've been transcoding some of my movies with Handbrake, and suddenly realized I've only been keeping one audio track. The default is usually Dolby 5.1 or 7.1 surround sound, but I don't have any surround speakers, just the plain old standard ones that came attached to my TV. Do I need to go back to the source and add in a stereo track? Or are TVs these days generally good enough at downmixing that it won't matter?

Sorry for the newbie question, but Googling hasn't turned up anything definitive. Thanks!

Woodstock
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Re: How many audio tracks?

Post by Woodstock » Thu Jul 04, 2019 3:20 pm

Most audio encoding systems used for video incorporate the stereo stream as part of the higher-channel encoding.

https://en.wikipedia.org/wiki/Joint_(audio_engineering) might help

Essentially, you have a channel with "all audio", and sub channels that are the difference between the given channel and the "all audio" channel. If your playback environment is mono, it only looks at the "all audio" stream. Stereo looks at the "L-R" stream to separate things.

When they go to "HD lossless", the HD stream is the difference between the lossy, normal stream, and a no-loss version, so that if your playback doesn't know about lossless, it still has something to play.

Blatherscribe
Posts: 8
Joined: Wed Jul 03, 2019 9:13 am

Re: How many audio tracks?

Post by Blatherscribe » Thu Jul 04, 2019 3:30 pm

So if I'm reading this correctly, the 7.1 audio track will be handled correctly for plain old stereo speakers if that's all I have? Why then is there a separate stereo track? (I'm not doubting you, I'm just curious about the reason for all the other audio tracks.)

Thanks for answering! :)

Woodstock
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Re: How many audio tracks?

Post by Woodstock » Thu Jul 04, 2019 3:52 pm

"Compatibility". While a stereo decoder is supposed to be capable of reading a higher-level track, it doesn't always work that way. If your players have no issue with it, though, you don't have to worry about having separate tracks.

The ripping program MakeMKV has been defaulted to separately writing a "lossy" and "lossless" track when it sees a "lossless HD" track, because some decoders DO get lost when they see the lossless track, unable to pull the lossy part out from the HD track. The author of that program decided it would be a good feature to offer, so he added it. So if a disk offers "TrueHD", for example, it will generate a TrueHD track, plus an AC3 track that is the lossy portion of the TrueHD track.

Blatherscribe
Posts: 8
Joined: Wed Jul 03, 2019 9:13 am

Re: How many audio tracks?

Post by Blatherscribe » Thu Jul 04, 2019 4:19 pm

Thanks, I think I get it now. My TV is fairly new, I just don't have a separate sound bar, so I guess it can handle things well enough. Same with the Roku.

Thanks again! I was not looking forward to re-ripping everything to add stereo tracks back in. :)

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