Help with understanding audio formats

[ra1024]

Can anyone point me to any good references on the audio formats these days? When I bought my receiver 5 years ago, it was mainly Dolby Digital and Dolby ProLogic but now it seems like there's a dozen formats which have replaced these.

I've read a lot the past 6 months on the hd world but never ran across audio formats much. Since joining these forums, I've seen a lot of discussion about the various formats in use on the br discs and wanted to get some background info.

Thx
RA

[ProvenFlipper]

www.audioholics.com

The forums there are great for anything related to audio.

[Damon Payne]

Originally Posted by ProvenFlipper

www.audioholics.com

The forums there are great for anything related to audio.

What are your specific questions? For example, I discuss bitrates and such in this article:
http://www.klipschcorner.com/Article...8-c1cf27507897

[ra1024]

Hey Damon,

I don't really know enough to ask an intelligent question yet

I guess the first place I need to start would be asking what are the main audio formats in use right now? I'm assuming dolby digital and pro logic are still in use but I think I've seen reference to a good dozen formats I don't recognize. I'm really just interested in the formats in use on dvd/hd dvd, br, and any hd tv broadcast signals.

Thanks for the reply,
RA

[LembasBread]

The most common consumer audio formats for movies is still AC-3 Dolby Digital followed by DTS. Their newest codecs, Dolby's TrueHD or E-AC-3 Dolby Digital Plus and DTS-HD High Resolution/Master Audio can now be used on HD DVD/BD. Uncompressed PCM can also be used on HD DVD/BD, but so far has been used exclusively by BD content providers (Sony and Disney).

There is another audio compression format for films called SDDS (Sony Dynamic Digital Sound) but is mainly used in cinemas and has no consumer applications. BTW, Dolby Pro Logic isn't an audio codec, it is just the matrixing algorythm for the 2 channel audio format of Dolby Surround or any 2 channel audio signal for that matter.

[ra1024]

Thanks for the info Lembas.

So would it be safe to say that AC-3, E-AC-3, and DTS-HD are the main formats you would look for in a new receiver?

Also, could you clear up something about PCM? I was under the impression that PCM was just a bitstream that a receiver would in essence just feed to the speakers ( after D-A conversion ). If I understand it, after decoding AC-3, E-AC-3, or DTS HD you would end up with something equivalent to PCM?

Thanks for the help.

[LembasBread]

Originally Posted by ra1024

So would it be safe to say that AC-3, E-AC-3, and DTS-HD are the main formats you would look for in a new receiver?

Pretty much. There aren't any available to consumers yet, but when they are released you'll want to make sure it decodes Dolby Digital Plus (E-AC-3), Dolby TrueHD, and DTS-HD formats (along with the usual Dolby and DTS codecs).

Also, could you clear up something about PCM?

PCM is still a codec, per say, but is raw, uncompressed digital audio that is the foundation of all uncompressed digital audio consumer and professional. It is the form that 99% of all digital audio is in before being compressed to Dolby or DTS and computer files like .wav and aiff are all PCM based. Also, CD audio is all PCM.

When you hear about HD DVD/BD players decoding audio and sending via HDMI and sending to a reciever, the player is decompressing the DD/DTS bitstream and encoding it as uncompressed PCM for virtually no signal degradation. When you have the audio being decoded by an outboard processor, I'm 99% positive that, baring any other signal processing, it is the decompressed bitstreams of DD/DTS, and not PCM, that are being converted to analogue to be sent to the speakers.

It is cheap to use for lossless sound on movies because the content providers don't have to pay royalties or compress the audio.
Check out more about PCM at:http://en.wikipedia.org/wiki/PCM