Effect of reducing DTSHD-MA core bitrate ?

[Libeluratio]

Hi everyone,

I was just curious about a thing:

If you reduce the core bitrate of an DTSHD-MA track from 1536 kbps to 768 kbps for example, I assume the resulting DTS-HD MA file will be smaller than the original.

But, by reducing the core bitrate, do we affect the entire file quality, or just the core quality ?

I mean, on a non DTSHD-MA capable receiver, I assume this will lower quality because it will just decode the DTS-core which is now 768 kbps instead of 1536 kbps before, right ?

But, on a DTSHD-MA capable receiver, will there be any differences between the first file (DTSHD-MA with 1536 kbps core) and the second (DTSHD-MA with 768 kbps core) ?


Thank you for lighting up my mind ;)

[sneaker_ger]

The lossless part uses informations from the lossy core so if you try to only re-encode the core at least quality will be reduced. Maybe it does not work at all or it becomes garbled (never seen anyone test it).

[filler56789]

But, on a DTSHD-MA capable receiver, will there be any differences between the first file (DTSHD-MA with 1536 kbps core) and the second (DTSHD-MA with 768 kbps core) ?

Nope, because a certified decoder will always decompress the lossy "core" bit-exactly.

If you reduce the core bitrate of an DTSHD-MA track from 1536 kbps to 768 kbps for example, I assume the resulting DTS-HD MA file will be smaller than the original.

Nope, it won't.

[mindbomb]

It's pretty straight forward. The lossless tracks are identical because they are have to be lossless. The lossy quality was reduced because of the reduced bitrate there. The file size is also reduced since the minimum bitrate was halved from 1.5 megabit. The difference is greater at 16 bit than 24 bit since 16 bit can reach lower bitrates more frequently.

[filler56789]

I stand corrected. I've run two test encodes on a 5min17sec, 16-bit, 2.0 audio track. The file with a 768kbps core has 47.5MB, whereas the one with a 384kbps core has 44.6MB. FWIW, the original .WAV file has 58.1MB.

[Libeluratio]

Ok, so the only differences between the DTS-HD MA files:

1 - 6 x PCM files encoded in DTS-HD MA with core bit rate set to 768 kbps
2 - 6 x PCM files encoded in DTS-HD MA with core bit rate set to 1536 kbps

is the size (1 is smaller than 2), and the playback on an non DTS-HD MA capable receiver (which is better with 2 than with 1), but on a DTS-HD MA capable receiver, the user will have exactly the same quality wether he plays 1 or 2, am I right ?

Thanks !

[mindbomb]

yes, i would say your assessment is correct.

[bxyhxyh]

Ok, so the only differences between the DTS-HD MA files:

1 - 6 x PCM files encoded in DTS-HD MA with core bit rate set to 768 kbps
2 - 6 x PCM files encoded in DTS-HD MA with core bit rate set to 1536 kbps

is the size (1 is smaller than 2), and the playback on an non DTS-HD MA capable receiver (which is better with 2 than with 1), but on a DTS-HD MA capable receiver, the user will have exactly the same quality wether he plays 1 or 2, am I right ?

Thanks !

I'm no expert here. But I really doubt this. Because DTSHD-MA contains core and difference right?
It adds difference to the core to play losslessly. So I think end result wouldn't be same.

[Libeluratio]

Except if the "difference" (you mean HD substream right ?) contains more info in the file 1 than the "difference" in file 2.

If it's not the case, that means that a 1536 kbps dts (simple, not HD-MA) could be better quality than a 768 kbps core DTS-HD MA (which is supposed to be lossless, because it is HD-MA)... ???

I dont know how to measure that..

[bxyhxyh]

Except if the "difference" (you mean HD substream right ?) contains more info in the file 1 than the "difference" in file 2.


Oh yeah you're right.