Design Goals and Implementation - Part 1

This is going to be a big one so I've split it up into a number of posts.  We'll start to delve into some detail relating to my goals for setting up my home theatre PC.

Below is a picture of what I'm trying to achieve.

So you can see from that that the PC will be doing most of the work including:

• DVD/Blu-Ray/CD player;
• Audio processor;
• Audio pre-amplifier;
• Video transport and partial image processor (the projector does the rest), and;
• Online/other media player.  For convenience, I want to rip all my CDs to the hard drive and be able to play them from there (WAV lossless format of course!).

Design Concepts

As stated in the first post, there are a number of concepts that I wanted to stick to with the design of this home theatre system.  These are detailed and expanded upon below.  Note that most of the initial design concepts were centred around integrating all the functionality into the HTPC; these have been merged into the one "Single Source" section below.


Single Source

The HTPC had to do it all.  Not out of necessity - just because I wanted to see if it could be done (plus I didn't want to be spending extra money on extra stuff taking up extra room when I could contain it all in the one box).  I know this probably goes against the audiophile angle of "separate components are always better", but the way I see it, all the HTPC components are separates (designed and built separately and by different companies) - they're just contained in the one box.  There are potential issues with this (particularly in regards to the audio), but more on this later.

For the HTPC to be doing all the work, I needed the following hardware and software components:

• Optical drive capable of playing Blu-Ray, DVD and CD.  I wouldn't mind being able to play DVD-A discs as well, but I haven't yet plucked up the courage to rock up to JB HiFi and ask "so where's your DVDA section?"  For those that have no idea what I'm talking about, that's probably for the best so we'll leave it at that!
• Audio card capable of high quality 7.1 channel analogue output.  Ideally, this would be capable of outputting a direct signal without trying to do any processing (i.e. upmixing, decompression effects etc.) on it.  Also, I have no intention of playing any PC games, so no need for the latest EAX processing.
• Software player for Blu-Ray/DVD/CD etc.  Windows Media Centre/Player can handle CD pretty well, can't handle Blu-Ray at all, and doesn't do any decoding other than Dolby Digital for DVDs.  I realise that there are 3rd-party decoders out there for DTS, but I'm not game to trust any of these as they seem pretty unofficial.
• Onboard graphics capable of HDMI output at full HD resolution (1920 x 1080).
• Enough storage to enable me to rip my music collection onto the hard drive and play it from there.  I'd also like to do this with my DVD and Blu-Ray collection, but at the moment there is no legitimate way to do this.  Token efforts have been made in the direction of "digital copy" features provided with discs, however these have not yet been widely adopted.

And of course all components to conform to the following standards:

• High-bandwidth Digital Content Protection (HDCP).  If any component in the pipeline of components from the disc to the display and speakers is not HDCP-compliant, the Blu-Ray disc can enforce downsampled playback;
• Advanced Access Content System (AACS).  A digital rights management (DRM) system for Blu-Ray;
• Protected Audio Path (PAP).  This one is solely aimed at those wanting to play Blu-Ray content on PCs.  As I understand it, this one took a while to get right which annoyed a significant number of people.

Conformance to the above standards is a primary design goal, since (if I can pull it off), there's a possibility of making a commercial venture of building and selling HTPCs and I want to do it right.  Mind you, even trying to do it legitimately, I ran into some issues, but more on how I solved those later.

"Clean and Green" Power

This is mainly to keep the Electro-Magnetic Interference (EMI) inside the case to a minimum so that it doesn't interfere with the production of the analogue audio.  A number of elements are required to attain this goal:

• All components to be minimal power consumption;
• Power supply not to be pushed to its limits so as to minimise power fluctuations;
• Tightest possible voltage regulation on the main power supply;
• No unnecessary components (eg. use onboard video instead of separate video card);
• Where possible, all high-current power cables to be routed around the outer edge of the inside of the case and not directly over or around the sound card;
• Large case to enable separation of components.  EMI falls off as the inverse of the square of the distance between components - meaning that even a little bit of extra space can make a big difference.

Play music without having to fire up the projector

This basically means getting a case with a display.  There are varying levels of displays available, I just wanted something simple that would show me information when I was scrolling through my music library relating to which album/artist I had currently selected etc.



So that's all my design goals in detail.  Next post, I promise I'll go into the components that I actually selected and the reasons why (and also highlight some mistakes/oversights that I made).

Stay tuned!