Code This

std::cout <<me.ramble() <<std::endl;

Archive for the ‘Home Theater’ Category

HD Audio Encoding, Decoded

leave a comment »

Disclaimer: Before I start, I just want to state that I am no authority on this subject matter.  I’m just a guy who has done a bit of research, so that hopefully you don’t have to.

I like to consider myself a fairly smart guy… modest too.  I’ve successfully setup/configured a number of home theater and car audio systems.  So my surprise when I found myself a bit befuddled when trying to properly setup my new home theater system was not without warrant.  It can be quite overwhelming when you consider the number of variables involved in the process.  It’s no wonder people dump hundreds (sometimes thousands) of dollars into having professionals take care of this process for them.  After spending hours reading online articles, discussions, and setup/user guides, I finally have my system configured correctly.  Hopefully I’ll be able to break the process down for you.

Unfortunately, since much of the new home audio and video technologies were released onto the market before they were ready, the process can be much more difficult.  From what I understand, products released within the last 6 months or so should be compliant with all the latest and greatest standards.  I’ll start with a breakdown of all the variables at play.

  • Video player technology: At this point, essentially blu-ray or DVD.  This guide is limited to HD audio, i.e., blu-ray.
  • Audio encoding format: This is were it starts to get fun.  Current formats include: Dolby Digital, Dolby TrueHD, DTS, DTS-HD, DTS-HD Master Audio, to name a few.  The two most current technologies, which are both lossless, include Dolby TrueHD and DTS-HD Master Audio.
  • Audio output type (from the player): Bitstream (encoded) and LPCM (decoded), for HD audio types.
  • Connection type: HD – HDMI or multi-channel analog; S/PDIF (digital) – Optical (toslink) or coaxial.
  • HDMI specification (if using HDMI connection): Current revision is 1.3a.
  • Point of decoding (what device actually decodes the encoded audio) – Blu-ray player, receiver, or even the TV.

And there’s also the fun fact that there are relationships going on between these different variables.

You need to start by considering your technology.  Most importantly, how old is your home theater receiver?  Does it have HDMI inputs?  If it does, great, your system can likely handle at least 1, if not both, lossless audio formats.  If not, does it have multi-channel analog 5.1 inputs? optical?  If it does have HDMI, is it version 1.3?  Lastly, does it support Dolby TrueHD or DTS-HD MA (at this point, it probably does not).  Here’s the list of scenarios, in order by preference:

  1. HDMI inputs
  2. Multi-channel analog
  3. Optical

Next we need to consider your blu-ray player.  You’ll need 2 invaluable resources for this: the player’s user guide, and cnet.com.  Cnet.com has tons of professional reviews on all the latest electronic equipment.  I strongly recommend you use this site when researching an electronics purchase.  It will also have all sorts of useful info on your blu-ray player.  Ideally, you want your blu-ray player to handle decoding the audio.  There are a couple reasons for this.  Blu-ray profile 1.1 (current standard) supports both primary and secondary audio and picture-in-picture.  In order to hear both audio streams, they have to be mixed.  To be mixed, they have to be decoded.  Also, as audio encoding standards change, it’s usually much cheaper to replace your player than your receiver (and possibly your speaker system).  Some people may say you want the receiver to handle the decoding because it is better at D/A conversion.  This is not true.  Decoding is done according to standard; it does not matter if it happens on the worst, or best, equipment on the market.  You need only be concerned that all audio processing happens in the receiver.  If your player cannot decode lossless audio, chances are your receiver cannot either.  Lets start with the ideal situation:

Your blu-ray player can decode all current audio encoding formats, and your receiver has an HDMI audio input.  Congrats.  Here’s what you need to do…  Hook the blu-ray player to the receiver using HDMI.  Configure your blu-ray player to decode (and mix) the audio streams.  It will send the audio in multi-channel LPCM format to the receiver.  Then just use the HDMI out on the receiver to hook to your television.  Easy enough.  If your player can’t decode the lossless formats and your receiver can (unlikely), configure it to output the audio in bitstream (encoded) format and hook everything up the same way.  You will not be able to hear any secondary audio data with this second configuration.

If your blu-ray player can decode all current audio formats, and your receiver does not have HDMI input, you have 2 options.  First, if the player has multi-channel analog outputs, connect it to the receiver using these outputs.  Then configure the player to decode the audio as above.  Your second option (and probably the better option) is to hook up your receiver following the steps below.

Let’s say your receiver is a little bit older (like mine) and doesn’t have HDMI inputs.  You’ll have to settle for optical.  You will not hear the lossless audio streams, they will be down-converted to plain ‘ole Dolby Digital or DTS 5.1 formats.  Unless you are an anal audiophile with high end equipment, or the type of person who has to have the latest and greatest for no apparent reason, it doesn’t really matter.  You won’t notice a difference anyway.  Here’s what you want to do… connect your blu-ray player to your receiver using an optical (or coaxial) cable.  Set your player up to mute HDMI audio output (HDMI carries audio and video.  You don’t want sound coming from your TV speakers and your surround sound system).  Configure the player to output the audio in bitstream (encoded) format to the receiver.

If your TV is like mine, it may have an optical out.  You probably don’t want to use your TV to provide the audio to your receiver.  I could find no documentation on what format (encoded or decoded) my TV uses to output audio.  You may also run into the problem of sound coming from both your TV speakers and your surround sound system.

A couple more things to keep in mind when purchasing/setting up a new home theater system:

  • Check cnet.com before you buy.
  • Configuring your TV correctly makes a big difference in picture quality and power consumption.  It is also very complicated to do.  Cnet.com has the ideal settings for most TVs available on the market.  You don’t need to pay someone $300 to do it for you.

Update: You may also want to check out this FAQ.  It provides some deeper explanations to some of the topics discussed here.

Advertisements

Written by Kris Wong

October 10, 2008 at 5:19 pm