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 Post subject: HDTV's as explained by n0b0dykn0ws
PostPosted: Sun Jul 13, 2008 3:56 pm 
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n0b0dykn0ws wrote:
Due to the recent activity in new posts on this subject, I'm creating this FAQ to hopefully be stickied. Feel free to ask questions, if you feel the answers are confusing, or if something hasn't been answered.

What are the different ways I can receive live HDTV signals on a PC?

This question is easy to answer. Currently there are four options: ATSC tuners, QAM tuners, CableCard tuners, and Firewire/IEEE 1394.

What is the difference between this four methods?

ATSC tuners can only receive over the air (OTA) transmissions. Most local TV stations now broadcast, at a minimum, using the ATSC DTV format. Out of the channels that do, most major network affiliates broadcast in HD when the source is available in HD.

QAM tuners take this method a little farther. There are main types of QAM signals: encrypted and unencrypted. Furthermore there is QAM 64 and QAM 256. *NOTE* Other variations of QAM do exist, but are rarely used by CableCos for broadcast. Unencrypted QAM, otherwise known as Clear-QAM, can also include SD DTV transmission. Most HD Clear-QAM will be limited to your local network affiliates.

CableCard tuners are fairly new to the arena of computers. There are two requirements for this method: a pre-built PC with a CableCard tuner and Windows Vista and the actual CableCard from your CableCo. The average cost for renting a CableCard is $10 US. This option will allow you to view all channels you pay for.

Firewire/IEEE 1394 recording is a bit trickier. The two requirements are a computer with a FW/1394 input and a set top box (STB) with an activated FW/1394 jack. To record/view shows through FW software must be installed. This software 'tricks' the STB into thinking a digital recorder has been connected. The major pitfall of this method is that most CableCos rent the STB with 5C enabled, potentially preventing recording or even tuning of certain channels.

So which one is best for me?

That's a tough question to answer.

If you have satellite and don't want to convert to cable, or can't, then an ATSC tuner is your only option.

If you have cable, but don't want to buy a special HTPC to watch all your channels, but still want some options, then QAM is a perfectly acceptable option. This will still allow you to view your local network affiliates at a minimum, and potentially most of your SD DTV channels.

If you want to be able to tune all HDTV channels received, and don't mind paying a premium for a HTPC with a CableCard tuner, plus the additional CableCard rental fee, then this method is worth a shot.

The FW/1394 option requires you to already have a STB in your possession. Out of all the options, it's actually the easiest to try if you already do have one.

So out of these four options, what products are available?

ATSC tuners are becoming more abundant. Hauppauge, Pinacle, ATI... the list goes on. The only real trick is to make sure you find one that has the latest generation tuner, and make sure your computer meets the specified minimum requirements.

Most ATSC tuners for computers on the market can also perform Clear-QAM tuning. So who's left out of the party? Media Center Edition users. Currently MCE does not support QAM tuning/recording support. QAM tuning under Vista is currently in BETA testing. As with ATSC tuners, make sure that you check the minimum system requirements. If QAM tuning is not listed on the product specifications, then check with the manufacturer, or back to this thread.

Currently there are only a handful of OEMs readying to offer CableCard HTPCs. Velocity Micro is currently shipping both AMD and Intel based systems with CableCard tuners.

As mentioned previously, FW/1394 requires software to perform the tuning. Check back soon for links to be provided.

What are the average system requirements?

Various manufacturers quote various requirements. Expect to need a 2.4 GHz (2 GHz for AMD) or faster processor. 1 GB of RAM with XP, 2 GBs for Vista.

For playback of recordings, the faster CPU, the better. Watching HD live on a tuner is smoother due to the decoding taking place on the card. On average HD recordings use 9 GBs of space per hour, so the bigger the HDD the better.

For even better playback, use a GeForce 8400/8500/8600 series, or a Radeon HD 2400/2600 series.

If you want to test your computer's playback capabilities you can download free test files.

What codecs are recordings captured in?

The official (H)DTV codec is MPEG2. However most files will be either .TP or .TS, in other words, transport streams.

These files are the MPEG2 video wrapped in meta-data containing information about the signal, and possibly even sub-channels.

So how do I play these files back once they are recorded?

A number of software players can playback .TP/.TS files, including, but not limited to, VLC and Cyberlink PowerDVD. The software that comes with the card will often include the ability to play back these files.

Some tuning software will output the recordings in MPEG2 natively.

There is also a free program called HDTVtoMPEG2 that will perform this function for you.

Can't I just go from my CableCo's STB to my tuner?

No. At least not if you want to watch/record in HD. The output from the STB will be NTSC.

What about satellite?

Currently in the US there are no legal satellite tuners for computers available.

Intel has been working with DirecTV to potentially bring a tuner to the market, but it will more than likely be similar to a CableCard 'closed system'.

You mentioned something called 5C earlier. What is it, and why should I be worried?

5C was the content protection scheme developed early on when FW was still be considered as a genuine display connection for HDTVs.

If 5C is present, it dictates if the program can be recorded, and if it is recorded how many times it can be copied, if at all.

In the past various lobbyists attempted to have the government require 5C to be present in all ATSC/QAM tuners. This was shot down at the time, but it might be pressed in the future.

The file is on my computer though, so how can the 5C dictate this?

In reality it can't. However, 5C can prevent you from recording the program in the first place.

What about CableCard recordings?

First of all, it's presumed the recordings performed on a CableCard equipped computer will be wrapped in DRM.

It's even been rumored that you will not be able to watch the recordings on other computers on your home network! Time will tell if this is true or not, if and when these systems become more prevalent in the home.

So get to the point. What product do you currently recommend?

The HDHomeRun by Silicondust.

It provides ATSC/Clear-QAM tuning/recording to any computer over your wired home network.

I've been hearing about SDV. What is it?

Switched Digital Video is an attempt to relieve bandwidth constraints on current cable systems.

Imagine, if you will, that your CableCo's head end office is like a giant file server.

With current cable technology the office sends out all files shared to all connected systems.

The way SDV differs is that instead of transmitting all available channels, or files in my analogy, the signal is only generated by request at the user's end sent to the office.

If SDV is implemented in my area, how does it benefit me?

Right now bandwidth for channels is being squeezed to the last 'drop'.

A number of the major CableCos have alleviated this, albeit in a minor way, by moving SD analog channels to digital transmission.

Without SDV a number of CableCos have even proposed eliminating all but very basic SD channels from the analog realm.

With SDV though, it's possible to move the restrictions to the office.

Another example would be a house with three TVs connected, as well as a broadband modem.

Each TV would be able to tune to a specific channel by sending a signal to the office, while the broadband modem maintains a constant bi-directional stream.

Assuming the equipment at the office can balance the load, you'd have more SD and HD offering than before, all at a higher bitrate than current offerings.

In the future when SDV is mature, your STB would have a second tuner to record a program while you watch another, or record two programs while watching a third prerecorded program.

This sounds familiar in a way. Haven't I seen this idea before?

You probably have. This is very similar to the way that Video On Demand operates.

VOD is possible due to the bi-directional signal between your STB and the office. It's similar to entering a URL or opening a file across a network.

I haven't been very happy with VOD though. Will SDV differ in quality and response time?

Hopefully the response time will be cut down with the first generation of SDV devices, but it's likelier this will occur with the second or third generation of the servers and boxes.

Right now bandwidth and server capacity/speed are a second priority for VOD. If a CableCo completely switches to SDV you should see higher quality than VOD.

As previously mentioned, this depends on the server capacity, and the number of boxes simultaneously attempting to connect to the service.

How can this be bad then?

For starters all distribution equipment at the office end as well as all boxes on the user end will be required to be replaced.

The truly devastating part is that any TV, or computer, connected to cable using a traditional tuner, or even a CableCard tuner, will not be able to receive the correct signal, rendering them all obsolete.

When can we expect to see a massive roll-out of SDV?

The most logical answer is not for a few years.

A handful of CableCos are currently testing in select areas, so a full scale roll-out will depend on the quality of service and customer reactions, not to mention the reliability of boxes and server equipment.

Will we see increased bandwidth on our cable modems?

Highly unlikely, or at least to say, not without a new pricing structure.

Only time will tell though, so we'll just have to wait and see how SDV pans out.


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