Benefit of DVD recorder with HDMI connection ?

It should at least keep the signal digital from DVD to tv. Presumably going via SCART means going to analogue, digitising in the display, scaling and then driving the display - going via HDMI should cut out some of the processing.

Given that the worst part of all pixel-based displays is the analogue processing, using HDMI interface should make for significantly better pictures. I'll temper that though, because the shortcomings of the analogue interface manage to conceal or reduce compression artefacts, so the pictures will be sharper and clearer, but may show more of the compression artefacts.

As is extremely obvious on an HDready set with inbuilt Freeview tuner. DVDs have a much higher bitrate than Freeview though, and hence far fewer artefacts, so the advantages here of HDMI should outweigh the disadvantages. At least one salesman has told me they prefer to showcase upmarket screens from DVD source rather then the inbuilt (digital) tuner for just this reason - this based on observation, rather than Alans quoted technical reasoning! Nice when the theory matches observations!

To those on this board making DVDs it's worth taking account that when choosing bitrate settings, and seeing just how much you can squeeze on, don't base your decisions on what it looks like on a 27" CRT if the client is likely to be viewing on a large high res plasma.

Surely the only bit-rate constraint to apply when making DVDs is that of the available disc space (i.e. try to - just - fill it), not whether the rate is "good enough" for any particular display? Better is better, whatever display it's destined for, surely?

Quite, and that has to be what we all aim at.

Incidentally, the explations I've given aren't theories, they're based on research work done years ago by colleagues and myself, using plasma displays long before Freeview was launched. We've know all this for at least 10 years, there's nothing new in it. And that's why I was always vehemently opposed to digital broadcasting being used to proliferate channels, when it could so easily have been configured to deilver fewer channels in really good quality. Sadly, the BBC was then, and still is, run by bean counters who wouldn't know a good tv picture if it bit them. Even more sadly, the unit I worked in was run by one such, so we were all ignored.

Mooblie - Fair point, and in many cases undeniably true. But in other cases it may be possible to split over more than one disc, or the perceived acceptable quality may even have dictated what bitrate can be gone down to, and hence the length to be aimed for in the final edit?

Imagine say, family videos, holidays etc, general home use which will undoubtably spread over more than one DVD. On the basis of a 27" Tv it may be decided that 2 hours/DVD is good enough, then a new plasma is bought, and that past bitrate decision is instantly regretted.

I just think that with such displays becoming more and more common, it's something to be bourne in mind, especially now with HDMI connectivity.

Not just the BBC - their standards are still higher than some of the other channels on Freeview, and at least (using 16QAM) their Freeview transmissions are more robust than many others (using 64QAM). Half the problem I suspect is how much the average quality of displays has improved since these decisions were taken, and what may have just about been OK then, now isn't.

I also thought that many of these policy decisions were taken by the government of the time, rather than the BBC solely? Interesting that it seems nowadays to be Sky who are most aware of quality issues, and hence their perception that there must be money to be made from HDTV.

Displays then were extremely good, big crts, hd capable and so on, including some very nice projectors. At the time decisions were made, we could clearly see compression artefacts on 14" tv sets, let alone on good monitors. And the government's decisions were taken after listening to advice from.......

Sky can afford the bitrate expense on their premium channels, they've got rich subscribers paying them. They've got so much bitrate that they can afford to multicast films, surely the worst waste of spectrum ever invented.

On this basis a 4 minute pop video filling 4.7gb would never play due to data overload.

DVD players come in several formats (+R, -R) of which some play better than the other with different player manufacturers/models of different ages, using different software/firmware and players on pc's with different capabilities.

When a dvd is produced it is expected to play on all manufactures models - whatever format, age or whether 'set-top' pc or playstation 2 etc.

This means lowering the bit rate a tad, for all round capability.
Too high a bit rate and pixelation/judder happens.

I understand that when pressing (as opposed to duplicating) the reflectivity of dvd is higher, leading to laser being able to cope with higher bit rate - which may mean higher quality.

I say 'may' as there are other encoding features to determine this, such as vbr/cbr and single pass/multipass.

Dave.

Ah! Agreed, then!

I was (wrongly) assuming a programme of some length (an hour or two), where my rule of thumb would apply. With short programmes, as you suggest, a mid-range bit-rate (NOT the maximum) is best for widest playability.

The maximum bit-rate that can be decoded in consumer players is usually accepted to be about 9Mb/s. I've seen some commercial dvds that get up to about 9.4 (and still played), but that's very rare. Generally, for consumer-made dvds, it's regarded as unsafe to go above about 8Mb/s.

OK,

so the HDMI connector is there to make sure the signal is kept as a digital signal and not having to go through an analogue to digital conversation, this sounds in theory to be a good idea, wonder why more dvd recorders have not got this connection, presumeably due to cost. Guys, thanks for the info.

Cheers John

Yes, that's true, but.....

HDMI in consumer kit is specifically for copy protection. The idea is that the signal never exists in analogue until it gets decoded inside the display (if at all). That way, the only signal stream accessible to the punter is the digital, encrypted data. So, you can't record it. The introduction of DVI in computing kit started this off, as a means of simplifying interconnections, but it's a rather expensive interconnection. HDMI is cheaper to implement, uses smaller connectors, and can easily have HDCP incorporated. And that's where it all makes sense.

Carrot and stick - "we'll give you this new connector which gives you better quality". True (it's the carrot). And (for HD discs, sky boxes etc) you HAVE to use it, or no picture at all - the stick.

Correct in all respects :(