Help deciphering the different 7.1 audio formats.

[peter_3388]

I am in need of assistance.
I want to know the difference between the different 7.1 audio formats that I see listed. Thanks in advance!

[DAve]

Hi Peter,

Perhaps be more specific.

For 7.1, Blu-ray Discs can use LPCM, DTS-HD or Dolby TrueHD.

Technically they can use Dolby Digital Plus, but none that I know of do this.

LPCM is simply uncompressed audio like a CD.

Dolby TrueHD is the Dolby version of audio that is compressed in a way that it can be returned to LPCM with no difference from the original LPCM.

DTS-HD Master Audio is the DTS version of audio that is compressed in a way that it can be returned to LPCM with no difference from the original LPCM.

DTS-HD High Resolution is a more heavily compressed codec which is lossy - so you cannot recreate the exact same audio representation as the original.

These days most if not all players sold can handle all of these formats.

If you have an older player, it may not handle some of these - though all discs have a fall back to Dolby Digital or DTS that can be decoded by any player.

Hope this helps - let me know if you have further questions.

[peter_3388]

It seems like there is a hierarchy to the sounds quality -
-LPCM is the highest quality
-DTS-HD Master Audio and Dolby TrueHD are compressed, but can be uncompressed to LPCM, thus just as good
-DTC-HD High Res is compressed, but cannot be uncompressed to LPCM, thus some loss

This is great information DAve. I wanted to know what to look for when I buy a Blu-Ray so I don't get duped! Thank you.

[DAve]

It should be no problem to find a player that can correctly decode everything.

You will find though that only some have analogue 7.1 outputs, which are needed for 7.1 if your amp or receiver does not handle HDMI.

Note that by and large the optical digital out will not carry 7.1 lossless - you need to use HDMI or analogue to get that.

Glad to help - maybe I should have this stuff on the site somewhere more useful!

[peter_3388]

What about the bit rate and frequency (kHz)?
Do they signify any kind of increased quality (or decreased if not listed)?
Thanks in advance again!

[DAve]

Most of the time the audio frequency is 48 kHz. If it is 96 or 192 (theoretically better) it is listed.

Usually only music titles are 96 kHz and Akira and Neil Young Archives are the only 192 kHz titles I know of.

24 bit is theoretically better than 16 - 24 bit is noted, 16 is default.

Lossy audio technically doesn't have a discernible bit depth since it can be decoded to any level of accuracy, and is never really the same as what was original anyways...

I think DTS can determine what the bit depth was that it was encoded from though... so you get some idea of the master.

In reality, most people are hard pushed to notice 16 vs 24, especially for the heavily processed movie sound.

[BluBlu]

Most of the time the audio frequency is 48 kHz. If it is 96 or 192 (theoretically better) it is listed.

Usually only music titles are 96 kHz and Akira and Neil Young Archives are the only 192 kHz titles I know of.

24 bit is theoretically better than 16 - 24 bit is noted, 16 is default.

Lossy audio technically doesn't have a discernible bit depth since it can be decoded to any level of accuracy, and is never really the same as what was original anyways...

I think DTS can determine what the bit depth was that it was encoded from though... so you get some idea of the master.

In reality, most people are hard pushed to notice 16 vs 24, especially for the heavily processed movie sound.

Hey, don't forget the audio-only releases from 2L, most of which also contain 192/24 in stereo and 5.1 in all three variants, TrueHD, DTS-HD Master Audio, and LPCM:

http://www.bigpicturebigsound.com/2L-Fo ... 1652.shtml
http://www.blu-raydefinition.com/news/t ... g-lyd.html