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Discussion Starter · #1 ·
Okay, after reading many, many posts about connecting HD sources to HD monitors via DVI, I gather that the physical layout is 24 - 28 wires. 24 bits of color information, clocked up to 1920 x 1080 x 60 pixels per second, and a couple of control lines, correct? That's 55.3 MHz for 720p, 62.2 MHz for 1080i, and 124.4 MHz for 1080p.

What are the length limitations going to be? If people are willing to pay $200 for 3m stereo cables, will they therefore pay $933 per meter for DVI cables? If you have an HD-DVD, HD-VCR, and HD set-top box, how will you switch all these devices?

DVI may make sense between a computer and LCD monitor, but it still needs work for an AV interconnect. My two cents.


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Quote:
Originally posted by Foxbat:
If you have an HD-DVD, HD-VCR, and HD set-top box, how will you switch all these devices?

DVI may make sense between a computer and LCD monitor, but it still needs work for an AV interconnect. My two cents.
An electronic switch box could be built with a repeater function to reconstruct the bits to provide a longer cable run, but compared to Firewire with HAVi it is still crude.


With Firewire and HAVi several pieces of equipment can be connected to other pieces of equipment over the network by just reading the channel data instead of switching connections.


DVI's only real use is for video processing boxes that improve the quality of standard HDTV. If a box only has DVI output, its a no buy decision. It can't be networked and will be an isolated island in a network of interconnected AV equipment.


Except for a few special cases, you have to give up a lot to use a DVI only box.
 

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Yes, with Firewire and HAVi, it'll be the interfaces that are crude... 1/2- http://www.avsforum.com/ubb/wink.gif I won't comment on the merits (or lack thereof) of spending $200 for 3m of audio cable, but I rather doubt that the DVI cable would be that expensive.


You could probably wander down to Fry's and have a look at DVI cables of various lengths. A quick perusal of the web found 5-meter DVI cables running about $50.


Seriously, I'm a big fan of FireWIre (I'm using it at this very instant), but IMNSHO it's a rotten choice for a display connector compared to DVI.


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Mike Kobb

(Formerly "ReplayMike", but no longer affiliated with the company; these opinions are mine alone.)


[This message has been edited by JustMike (edited 09-06-2001).]


[This message has been edited by JustMike (edited 09-06-2001).]
 

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I agree that HAVI, as it is mostly envisioned, is likely to create quite crude and simplistic control systems. They'll mostly tend to be least common denomator with limited resolution in order to support lower res displays.


However, all's not lost. PC based control systems like my CQC product should be able to act as a controller on a HAVI network, with the appropriate Firewire board. In that case, you'll get the convenience of a single, daisy chained interconnect, plus a powerful, PC based control system with high resolution graphics, powerful macros, etc...


I'm keeping my eye on it and seeing what happens. So far its not worth messing with, but it could happen eventually.



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Dean Roddey

The Charmed Quark Controller
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www.charmedquark.com


If it don't have a control port, don't buy it!
 

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How does FireWire (IEEE 1394) at 400,000,000 bits per second keep up with 1080P? Or even 1080i? Is the data still compressed?

1080P is almost 3,000,000,000 (3 *billion* bits per sec.)


There is no lossless compression that will do this reliably so are they downrezing over firewire or is it being passes around as an MPEG2 bitstream?


Either way, once decoded, only DVI (of the two choices) can handle the bit rate.


Point me to another thread if I'm off base. I know DVI and Firewire, but not the particulars of their application to HDTV.
 

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Ken, you're right.


There are basically two schools of thought:


1) Put a lot of smarts into the display. This includes an MPEG-2 decoder and (if you're HAVi Level 2 compliant) a Java Virtual Machine (JVM) to run the user interfaces of your various connected devices.


2) Put limited smarts into the display (just a DVI connector and associated electronics, essentially). Keep the smarts in the individual set-top boxes (including MPEG decoding and the user interface).


There are plusses and minuses to both approaches. In my opinion, DVI is the winner. I'll summarize the plusses and minuses and tell you why I favor DVI.


If you choose approach #1, there are several benefits. You have one type of cable and connector to hook up everything in your entertainment system. From your CD player to your HD set-top to your PVR to your display, everything is hooked up via FireWire. If everything in your rig is HAVi (Home Audio Video interoperability) compliant, then they all "talk" to each other in clever ways, and your display has all the smarts needed to display the interfaces of the various components. Theoretically, the system cost is reduced because you're only paying for one MPEG decoder in the display (rather than one in each set-top), and the set-tops also don't have to have the OSD hardware to do the user interface. All your 1394 devices are connected into what is essentially a "network", so your devices don't all have to route through a specific "hub" component, or to multiple inputs on your display.


Approach #1 also has some serious disadvantages. First among them is that (in my opinion) HAVi is never going to work for devices of any complexity. I've discussed this on other threads (do a search for "HAVi"), but basically if I as a set-top box designer were limited to the capabilities of a HAVi-compliant display, I wouldn't be able to make a very interesting interface. They've tried in the HAVi spec to provide some good functionality, but it's nearly impossible to foresee the needs of every device into the future. This type of connection is (for instance) completely useless for video games or any other device which uses graphics acceleration hardware to render its displays or content.


Also a disadvantage for 1394: let's say that MPEG-4 actually goes somewhere. Now you have a display with a 1394 connector and an MPEG-2 decoder in it. Now what? They're not compatible, and you're stuck buying a new display (or perhaps upgrading a connection module if you're incredibly lucky).


So, what about approach #2? Well, DVI is simply a video interconnect standard. Nothing more. All the smarts for decoding the incoming video signal (MPEG-2, MPEG-4 or whatever else) is in the set-top receiving the signal. The same set-top overlays whatever type of user interface its designers can concoct -- possibly including hardware assistance to do fancy stuff -- and squirts the bits over DVI to the display. This model is fully compatible with video games, future video encoding standards, and hardware-assisted user interfaces.


Disadvantages? Well, DVI is a point-to-point interconnect. It's not a network. So, if you want multiple devices to connect to your DVI-equipped display, you need either multiple inputs on the display, or some sort of switching capability, in your receiver or an external switcher. DVI doesn't carry audio (although there's at least one proposal to add it), so if you plan to use the audio capabilities in your display, you need to run audio cables as well. The DVI cable itself has several times the number of wires in a FireWire cable, so one can expect the cable cost to be higher. It also operates at higher frequencies, so it may be more picky about long cable runs. DVI is not recordable, so a set-top would also need a 1394 output for sending data to a recorder.


In summary, I think 1394/HAVi is a noble goal. Like many noble goals, it's also impractical. I think 1394 is a fine interconnect for dealing with digital streams between components. It makes a lot of sense, for example, as a recording connection between an HD set-top and a digital recorder. However, because it can't carry an uncompressed HD signal, it can't be used to carry the user interface of a set-top box (unless you generate your UI and then MPEG-2 compress it, which is just a dumb idea). Therefore, to make an interface work via FireWire, you need something like HAVi, which is guaranteed to have compatibility issues and performance limitations, and to place unnecessary and unwanted constraints onto the designers of hardware products whose stock in trade is developing differentiated feature sets to attract customers.


Recently, major set-top makers (DirecTV, Echostar/Dish, Cable Labs) announced support for DVI as the display connection, maintaining 1394 as a recording connection. I believe they did so because the recognized the issues I described above. JVC has shipped a DVI-equipped display (the D'Ahlia rear-projection HDTV). Mitsubishi, on the other hand, continues to back 1394/HAVi, at least in some comments. So, the adoption of DVI as a display interface is still up in the air.


I hope this proves somewhat useful.


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Mike Kobb

(Formerly "ReplayMike", but no longer affiliated with the company; these opinions are mine alone.)
 

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Thanks Mike!

That's pretty much what I assumed knowing just a smidgen about each. I can say from experience that anyone who sees a DVI interface is likely to reach for their wallet. There's no substitute for knowing the exact color of each and every exact pixel!


MPEG decoders are still being perfected and I would prefer it be in my STB that I upgrade much more often than my display. I suppose TV's could have upgradeable firmware but that model doesn't sound right.


Perhaps TV's will wind up having both just like they have composite and s-video or component. I'll bet the high end solutions will gravitate to a DVI based DVD source and/or DVI cable/sat./ota STB. It's just like you say - the STB makers will put better and better features into their STB's to woo new customers.


If people could see DVI, they would quit whining about obsolescence and start asking about a Group Purchase! http://www.avsforum.com/ubb/smile.gif

Ken
 

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Hi All,

I like too mention one little fact that everyone has left out. Some of the newer MPEG2 decoders are being implemented in FPGA(Field Programable Gate Arrays). The new Mits integated HDTVs has a memory card slot in the back. The Memory cards will be used to upgrade the internal computers of the sets with updated HAVi device connection information and possibly new programs for the FPGAs.

This little information really makes IEEE1394 with HAVi interface a much better deal then DVI.


The intention of DVI interface is to prevent anyone from using a Digital VHS-VCR. I doubt that you will every see a IEEE1394 port on the same STB as a DVI interface.


DVI interface is intented to remove your fair rights as decided by the BataMax Case. The intention of the MPAA is to stop you from recording anything. Yes there would be PVR devices in the DVI STBs, but they would only be good for time-shifting a few hours of HD.


A DVI eqiup set will have no better picture then a IEEE1394 because they will both use the same MPEG decoders. It is most likely that IEEE1394 set will have better picture because the MPEG decoder is in the display device.


IEEE1394 device will be lower cost. Only one MPEG decoder is needed for the system. I wany my Digital VHS-VCR. So my choice is the IEEE1394 Firewire interface.



DVI just sucks!




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Bruce.in.Cary
 

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Discussion Starter · #9 ·
Mike: I don't think the DVI cables are going to be that expensive, they should be somewhere in the UltraSCSI price range. Rather, I was poking fun at the thought of Monster Cable (or some of the other ultra-high-end, esoteric cable makers) justifying their high prices based on the number of conductors. Someone does make gold-plated TOSlink cables after all!

If DVI were just a one-way connection, switching wouldn't be too too bad, but HDCP requires bi-directional communications. I would think that putting DVI/HDCP switching capability into an AV pre-amp will add $50-$200 per connection.

Firewire looks like the clear winner in setting up any multi-source AV setup. DVI works for PCs. Send DVI/HDCP back to the drawing board, er, CAD station...


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HAVi Java Source code for a PVR, time shift, and network monitor are at
http://www.vividlogic.com/hbx/


Could someone please run that code and post an example of what a HAVi GUI looks like from that code (if the code shows a GUI). There is also a HAVi Java programing book on the page. It would be interesting to see the best examples from that book.


Even if the standard HAVi GUI is ugly, this is version 1.1 and it will get better. The ability to network the house and have a large computer display AV system controller is much more important to me.


At least with the HAVi API there is a chance that we will start to get a consistent GUI standard between all of the many AV components. That's important for people that have a life that does not revolve around complex technology.


Its also important to not need six remotes to run your AV system. DVI looks like it keeps us in the past with islands of AV in the house, multiple remotes, and widely different non-integrated GUI's.
 

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HAVi in a way is kind of caught in a catch-22, it seems to me. Basically, the kinds of devices that are 'worthy' of quality control already have serial port control for the most part. Of course that has its problems and single, daisy-chained control cable would be nice and all that, but still the control is there. And you can do very nice control software based on that serial control for the most part.


So, the question is (regardless of other issues or shortcomings that HAVi might have) will the kinds of devices that already don't have non-IR control support be any more likely to provide a HAVi interface? I'm not sure, but since its likely to be based on price, will a HAVi interface be cheaper than a serial port? I guess in some wasy it will if there are standard chipsets that can handle some of the grunt work, but overall I'm not so sure that some of the devices that we commonly use will have ubiquitous HAVi type support any time soon.


And if you have one device that isn't controllable, and the ones most likely not to are the ones that you most often have to interact with like DVD players, cable boxes, sat boxes, etc..., that pretty much prevents you from having a strong control system in your theater. IR is a fallback but it'll never allow you to create truely powerful control, that can sense when things go wrong and try to correct for it and such.



On another topic raised, about the 'standard HAVi interface'. I think that any powerful control system, such as I aim my CQC system to be, cannot depend on auto discovery except for the most primitive control of devices. If you want a slick system, you'll want to have drivers for particular devices that really understand them and their caveats (and they all have them.) For instance, having an auto-discovery of a projector's ability to let you choose a memory is nice. But if your software doesn't understand that that particular projector goes off into limbo for 10 seconds after it sees a new signal type, and will therefore fail to accept a memory selection during that time, it won't be as robust as control system.


I think that auto-discovery of devices and basic functionality will still help someone like me. The most basic functionality such as turn it off/on, play, stop and whatnot are commonly used in macros and being able to control those things even without an explicit device being available will make things like CQC more widely applicable. But those folks who want some slick and powerful control will probably prefer to have the control system be pretty smart about what the device can do and how well/badly it does it.


Then again, I could be completely wrong. I've only briefly scanned the HAVi web site a few times. But these things have begun to become obvious to me as I've spent the last year really thinking about control issues as I've been developing the CQC software.



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Dean Roddey

The Charmed Quark Controller
[email protected]
www.charmedquark.com


If it don't have a control port, don't buy it!
 

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Quote:
Originally posted by Bruce Embry:
Hi All,

I like too mention one little fact that everyone has left out. Some of the newer MPEG2 decoders are being implemented in FPGA(Field Programable Gate Arrays). The new Mits integated HDTVs has a memory card slot in the back. The Memory cards will be used to upgrade the internal computers of the sets with updated HAVi device connection information and possibly new programs for the FPGAs.

This little information really makes IEEE1394 with HAVi interface a much better deal then DVI.
Well, upgradability is definitely a good thing, but in my opinion it's insufficient in this case. What if the MPEG4 decoder won't fit in your FPGA? What if I want to do a cool user interface for my product, but it requires more computing power than is present within the display devices? Then you're just SOL.


But, it gets worse: obviously, nobody is going to implement something like the 3D "Emotion Engine" in the PlayStation 2 (10.4 million transistors with 128-bit bus widths and such) in an FPGA anytime soon. I shudder to think what's in the XBOX.


Clearly, a display is going to need some sort of "raw" input for images computed on some other device. You could use analog component inputs, I guess, but why not use DVI?


The claim that DVI is an attempt to quash home recording rights strikes me as paranoid. I think the obvious answer is to do what I'm doing: don't buy a set-top without recording capable outputs. DirecTV and Echostar have all but promised that they will be building STBs with both types of outputs, as has Cable Labs.


I'm sure that HAVi will continue to be improved (assuming that it doesn't just plain die), but I really doubt that it will ever be sufficient for all set-top needs, since the set-top needs will be evolving at least as quickly.


One possibility I could foresee actually buying: a very high-powered HAVi display implementation with lots of memory, a fast CPU, a world-class JVM and a state of the art MPEG decoder. Put that in a little box with a 1394 port on one side and a DVI port on the other. Then your HAVi implementation is easily upgradeable without modification to your display.


Finally, Foxbat, I'm not sure how you're coming up with $50-200 per connection, but you may be right that switching it in the preamp could be expensive. It would certainly be BIG -- the DVI connector is hardly compact.


Anyway, if people seriously believe that HAVi will be a workable solution, then by all means seek out components that support it. I'm skeptical. I'll certainly be checking out HAVi at CES this year. I hope it looks better than it did last year and the year before...


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Mike Kobb

(Formerly "ReplayMike", but no longer affiliated with the company; these opinions are mine alone.)
 

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Everyone try to remember that if HDHT (High Def Home T)is your hobby then the pursuit of ultimate picture quality within your budget is the name of the game. This means separates whenever possible.


1. You want the best display you can afford that also fits your WAF and other needs.

2. You want the best sources you can afford (DVD,DSS,OTA)

3. You want other gee-wizbang capabilities (HAVi, PVR)


I'm sure this list could be added to and expanded on, but one thing is certain. They move ahead and change at different rates. You don't want a case where the display you like best has an inferior mpeg decoder. (Chroma bug, etc.)

Even if you gotta have HAVi, you'd want a HAVi compatible mpeg box with a DVI or similar connection to your display. That way when Stacey and Friends have their shootouts you can upgrade like you upgrade your DVD player now.

Don't be so myopic as to see only the copy protection aspects of DVI. A digital video interface such as this is a great improvement over analog component and RGB! Do a search on SDI and learn a bit about the benefits of a pure digital path.

If the result of MPAA paranoia is that ultimate quality digital interfaces (DVI) are pushed to mainstream price and availability then where's the downside?

If you want to compare DVI to something it should be s,component, and rgb connections. For a preview of the differences read TommyBoy's Scaler Review and look at the SDI Vigitec case.

Ken
 

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Quote:
Originally posted by Foxbat:
I don't think the DVI cables are going to be that expensive...
I think a 1 meter cable was in the $80 range when we went to buy some...





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-- Keith Jack

-- author: Video Demystified
 

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Quote:
Originally posted by JustMike:
Well, upgradability is definitely a good thing, but in my opinion it's insufficient in this case. What if the MPEG4 decoder won't fit in your FPGA?
Takes us a rack of FPGAs to do our MPEG-2 and MPEG-4 decoding emulations, but the biggest thing is speed limitations. Things get real nasty real fast when you start processing multiple streams simultaneously to handle PIP and PVR functions.


Quote:
Originally posted by JustMike:
One possibility I could foresee actually buying: a very high-powered HAVi display implementation with lots of memory, a fast CPU, a world-class JVM and a state of the art MPEG decoder. Put that in a little box with a 1394 port on one side and a DVI port on the other. Then your HAVi implementation is easily upgradeable without modification to your display.
I was part of a presentation at the Intel Developer Forum last week that offered just a solution. The key thing is that boxes for the living room must not use a fan -- too noisy for most consumers. Yet you don't want to use for than 50% of the CPU power today to allow room to grow in the future. So that means hardware decoding...




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-- Keith Jack

-- author: Video Demystified
 

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Quote:
Originally posted by kjack:
The key thing is that boxes for the living room must not use a fan -- too noisy for most consumers.
Tivos have fans (and hard disks and everything else that makes a computer). I have two of them next to my TV and can't hear them unless I'm right next to them.
 

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Discussion Starter · #17 ·
Quote:
Originally posted by kjack:
I think a 1 meter cable was in the $80 range when we went to buy some...
Keith,

I've never seen a DVI cable in person. How thick is the cable? $80 for 1 meter? I'm sure most of the cost is in making the connectors, so additinal lengths shouldn't add too much to the cost. Most of us with home theaters have more than 3 ft. between our displays and sources. I just shudder to think about a bunch of 1/2" cables snaking through my entertainment center.


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Quote:
Originally posted by JustMike:


One possibility I could foresee actually buying: a very high-powered HAVi display implementation with lots of memory, a fast CPU, a world-class JVM and a state of the art MPEG decoder. Put that in a little box with a 1394 port on one side and a DVI port on the other. Then your HAVi implementation is easily upgradeable without modification to your display.


There is at least one low cost (I think $24) chip on the market that does MPEG-2 and MPEG-4. That could be inside the monitor.


There are compression methods that have already been announced that are twice as good (half the bit rate for same image quality) with more improvements to come. Obviously this could cause problems with a hardwired decoder architecture.


I agree that the best of all worlds will be a flexible external box with Firewire/HAVi input and DVI output. The state of the art is no where near maturity and flexibility is important at this time.


At least with HAVi, we can at least have the option to use a computer to control all the equipment. The on screen display of DirecTv is nice, but it irritates me with its covering up the picture. I may not like having to look at two displays, but at least the option will be there.
 
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