HD picture quality, vs SD picture quality

Posted on April 28, 2007 by Stephen Dawson

The issue before last of Sound and Image magazine carries my article comparing the picture quality of SDTV and HDTV. In brief, I captured snippets of both versions of the same programs on a high definition PVR (the Strong SRT-5490), downloaded them to my computer, then took a number of matching frames for the comparison.

The article came out quite nicely, I thought, but in the translation of the stills to the printed page, I thought the differences weren’t quite as clear as they were on my computer screen. With my similar article in the current issue, with Blu-ray vs DVD, the differences in the comparison shots are a lot clearer.

Anyway, I’ve placed the whole article, complete with the comparison photos, here: Standard Definition TV vs High Definition TV: Is the latter really better than the former?

UPDATE (Saturday, 28 April 2007, 11:49 pm): I’ve also improved and uploaded an article I did for The Canberra Times on the 576p standard of ‘HDTV’: ‘When HDTV is not HDTV: 576p is not high definition‘

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We need a videophile’s High Definition Digital TV Receiver

Posted on April 26, 2007 by Stephen Dawson

I’ve been struggling to get my head around this for some time. The problem has been a lack of replicable test signals. But I think I’ve got it nailed, at last.

I was watching a late night movie on ABC TV recently. Normally these are old black and white things, but this one happened to be in colour. It wasn’t particularly good. This was on digital TV, and I was using a Strong SRT-5490 HD PVR. This was feeding via its DVI output to the HDMI input on a BenQ 1080p DLP projector. But not directly. The signal was going via a DVDO iScan VP50, one of the best video processors in the world.

The output of the Strong was set to 1080i, and the VP50 was converting this to 1080p.

A necktie illustrates deinterlacing problemsAs I was watching, I noticed that there was a moire pattern on the fine texture of the necktie of one of the characters. So I recorded a snippet of the video.

Many of these late night movies are of appalling quality, primarily because the video appears to have been derived from an NTSC source, and converted to PAL.

You can convert NTSC to PAL by doing some heavy processing: reversing the 3:2 pulldown so that you end up with the original film frames, and then recompiling them into 25 frames per second PAL. But these movies are rarely like that. Instead, they are converted to PAL directly from NTSC, with most of the frames showing heavy interlacing. That is dealt with by video processors by eliminating the second field — at least for moving parts of the picture for high quality processors such as the VP50 — further softening what is already pretty fuzzy video.

But this particular movie didn’t suffer from that problem. It appeared to have been telecined from the original film, and so was actually progressive in nature. I downloaded the short recording onto my computer, and examined the video closely. Yes, it was definitely progressive.

At this point, I would suggest that you read my article on problems with DVD player deinterlacing, especially the section headed ‘Deinterlacing video-sourced content’. As you will see from this, a moire effect often happens when fine patterns on progressive source video are inappropriately deinterlaced using the ‘bobbing’ method. That’s what seemed to be happening in this case.

The ABC TV program was broadcast as 576i. The procedure for converting 576i video to 1080i is to first convert it to 576p (ie. deinterlace it) and then scale it up to 1080. I’m fairly confident that the Strong SRT-5490 just bobs all 576i material on the way to upscaling it to 1080i. I strongly suspect that this is also done by all HD TV receivers on the Australian market. I shall confirm this over time.

So what we really need is a HD TV receiver that can either output 576i over a HDMI output (DVI outputs do a weird output when set to 576i, which isn’t compatible with all the displays I’ve tested), or incorporates high quality video processing that checks the interlaced status of the actual video, and then weaves progressive source material.

UPDATE (Monday, 30 April 2007, 4:26 pm): Further on this, with real proof, in entry ‘Proof of crappy video output from HDPVR‘.

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1:1 pixel mapping – why your 1080p display should have it

Posted on April 18, 2007 by Stephen Dawson

Well, and poorly, mapped pixelsLast night I started working on a blog entry on this subject, but soon after I started I realised that I was putting in too much work to just give it away. So this is just a brief taste. Full details will be in a forthcoming issue of Sound and Image magazine.

The picture to the right consists of details from two closeup photos I took last night of a 1080p LCD display. In both cases I was feeding a 1080p test signal from a DVDO iScan VP50 to the display. The test signal was alternating black and white lines for the entire 1080 line height of the picture.

The picture on the left shows the excellent result achieved when I enabled 1:1 pixel mapping in the display. The picture on the right was with the default setting of the display, which scaled up the picture slightly. Obviously one is far more accurate than the other.

In the article I have used a analogy of the ‘beat’, the cyclic volume variation when two notes are played which are very close to, but not quite exactly, matched. That led to a discussion with my editor of the differences and similarities between the auditory and visual worlds. Naturally I had some thoughts on the matter.

Both musical beats and the display example in the photos just come down to interference patterns. You could make the reverse analogy and say that a beat generated by two slightly mismatched tones is actually an aural moire pattern.

However in the visual field the effect is far less obvious than the musical field. It’s amazing how much rescaling and conversion of video that can take place with remarkably little impact on the picture. Try to do to music the stuff that we do to video, and it would sound like crap.

I think its because of the differences between the ways our eyes and ears work. The latter do divide sound up into several frequency ranges, with different parts of the ear responding to different bands, but in the end it is all woven together and we get a seamless capture of up to ten octaves.

Our eyes only have a range of one octave, so that immediately rules out doing anything artistic with light in a way akin to music. It’s the coincidence of harmonics that makes musical harmony work: the second harmonic of C is almost identical to the first harmonic of G — there is just 0.89 hertz difference between them for Middle C and the G above it, and if you listen carefully you can hear the slow beat; and there is 1.18 hertz difference between the third harmonic of Middle C and the second harmonic of the F above it.

The other difference is that our eyes treat brightness and colour very differently. It is colour, of course, that is the equivalent of tone in sound. But we do not see a continuous spectrum of colour in the way that we hear a continuous spectrum of sounds. There are three colour bands, and all the light frequencies near to the centre point of one of those bands are lumped together and captured by just one of the three types of pigmented colour receptors in the eye.

What our brains tell us is a smooth range of colours is actually the results of mixing three levels of response from the three types of receptors to three bands of frequencies. In fact, you can take two sets of three frequencies, and if the levels are adjusted correctly, you can make them both look the same, although they would measure very differently with a suitable instrument.

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ABC Digital TV switches to full surround sound — sort of

Posted on April 17, 2007 by Stephen Dawson

I was watching ABC digital TV last night when I happened to notice that the home theatre receiver was indicating that the incoming digital audio was 5.0 channels, rather than the usual 2.0. To double check, I recorded a bit and transferred it over to my computer.

The Wild and the Willing (1962)Remember, ABC TV is unusual in delivering two audio streams. There is an two channel MPEG2 stream at 256kbps, and a high bitrate Dolby Digital stream. This runs at 448kbps (the maximum provided on DVDs, although Dolby Digital actually supports up to 640kbps) and last time I checked was in two channel format.

But now, I see, it is delivering 5.0 channels (same bitrate). You won’t notice this unless you have made your set top box default to the Dolby Digital audio track, if available.

Of course, Dolby Digital 5.0 is merely a delivery system. Whether the sound will be surround or not depends entirely on what is packed into those five channels. The show I checked, for example, was a quite forgettable late night movie called The Wild and the Willing. Forgettable except that it was the debut of a number of fine British actors, including John Hurt.

The packing of the stream may be five channel, but of course the content was only mono.

There is one problem with this. I routinely have the input of my receiver to which the set top box is connected switched to Dolby Pro Logic II decoding, so as to extract any surround content that may be encoded into the two channel source. But this won’t work on 5.0 (or 5.1) signals. I doubt that it will with any receivers. So for those shows, it’s necessary to switch back to the MPEG2 audio.

UPDATE (Wednesday, 18 April 2007, 11:21 am): Well, that was short-lived. I had the ABC on again last night, and the Dolby Digital track was in 2.0 channels. They must be experimenting.

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Who’d ever have thought it

Posted on April 14, 2007 by Stephen Dawson

I was perusing, as I so often do, the Internet Movie Database when I stumbled upon something quite surprising. It was that the 1929 Disney animation, ‘The Skeleton Dance‘, was banned in, of all places, Sweden. Clicking on the provided link, I discovered a whole bunch of startling bannings in Sweden (there are 229 in total, according to IMDB):

Incredible!

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The HD format war already coming to an end?

Posted on April 11, 2007 by Stephen Dawson

I’ve been saying pretty much from the start that eventually there will be dual format HD DVD/Blu-ray players. But I wasn’t expecting it for maybe three or four years. Well, the pace of technological improvement continues to accelerate, and already there is a hybrid HD DVD/Blu-ray player from LG (in the United States, anyway). Apparently the LG BH100 is less than perfect, but that’s unimportant. What is important is the proof of concept.

Meanwhile, Warner Bros (which supports both HD DVD and Blu-ray) has announced a new hybrid disc with both HD DVD and Blu-ray content. If these work okay that will deal with the one remaining problem of the two formats: inventory management.

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The dirtiest joke ever on prime time TV?

Posted on April 10, 2007 by Stephen Dawson

Sneed's Feed & Seed, Formerly Chuck'sWe all know that ‘The Simpsons‘ is hilarious. And it sometimes pushes the boundaries for taste, usually for those who don’t quite get it.

I recall hearing some young fellow ring up the John Laws radio talk back program last year complaining about how negatively Australia had been portrayed on ‘The Simpsons’. Presumably he was talking about the episode ‘Bart vs. Australia‘ (Season 6, Episode 16), in which Bart has to go to Australia to receive the alleged traditional punishment for his misdeeds of the boot in the behind. Of course, ‘The Simpsons’ is just as unkind to the French and the Albanians, the Japanese, the Scots, and just about every other nationality you care to name, not the least Americans.

But the immediate reason for this post is that this evening, at 6pm, the regular repeat episode of ‘The Simpsons’ was ‘E-I-E-I-(Annoyed Grunt)‘ which contains what James Lileks once called ‘the filthiest joke ever broadcast on network TV’. I certainly didn’t get it until I read that post. Do you?

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Blu-ray vs HD DVD – is Blu-ray hobbling itself?

Posted on April 10, 2007 by Stephen Dawson

Some years ago I received a DVD player for review. Before I had a chance to get it out of the box, I received a call from the PR company. The previous reviewer had accidentally left a DVD in it, so could I post it to him? Sure, not a problem.

In case that reviewer happens to be reading this, don’t worry: I can’t remember who you are, or even which particular brand of DVD player I was reviewing. You see, the said disc turned out to be an adult movie (I shall avoid the ‘p’ word so as not to tempt Net Nanny and the like to blacklist this site).

Now I read that Sony apparently says it will not source its Blu-ray discs from disc replicators which also produce discs for the adult film industry. Apparently Disney has the same policy.

I have been fairly dismissive of claims that either Blu-ray or HD DVD is significantly superior to the other. Blu-ray is perhaps a little more attractive because of the greater disc capacity. But so far it has largely negated that by using the MPEG2 video compression scheme for most releases (certainly, all that I’ve seen), rather than the more efficient systems available (all the HD DVD discs I’ve seen use the more highly developed, and much newer, VC-1 system).

In order to achieve its higher capacity, the Blu-ray crowd have re-designed the discs themselves. DVDs, HD DVDs and BDs (Blu-ray Discs) are all 1.2mm thick. But DVDs and HD DVDs have their data half way down through the disc’s thickness: that is, they have a 0.6mm layer of transparent plastic on top of the data. BDs have the data much nearer to the playing surface, just 0.1mm down. To overcome possible damage to the data from scratches and the like, BDs use a much harder plastic.

This closeness of the data layer to the surface is what allows the higher data density.

Toshiba has often touted the more traditional structure of HD DVDs as an advantage of its format. It argues, probably correctly, that current DVD production equipment can be used to produce HD DVDs, rather than the expensive new equipment required for Blu-ray. I haven’t found this a persuasive argument because whichever the format, disc production costs are a tiny percentage of the release costs of any movie.

But this story puts a new slant on it. If you have invested in expensive new equipment for BD production, would you be prepared to eliminate from your customer list both Disney and Sony (which owns the Columbia, TriStar and MGM movie catalogues) in order to press Blu-ray adult films? DVD production equipment, though, is relatively cheap.

So expect high definition adult material to appear on HD DVD rather than Blu-ray. The more cynical may suggest that this will ensure the success of HD DVD and the eventual demise of Blu-ray. I doubt it myself, but it will be interesting to see what does happen.

UPDATE (Wednesday, 11 April 2007, 12:22 pm): Looks like this isn’t going to be the case after all.

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Putting pressure on TV cinematographers

Posted on April 4, 2007 by Stephen Dawson

Variable focus in Medium It isn’t easy to be a TV cinematographer these days. The other night I was watching Medium on high definition TV. The pre-titles opening scene was, as usual, one of Alison Dubois’ dreams. Mrs Dubois is the titular Medium, and every week she solves some murder in Phoenix, Arizona, thanks to her ability to communicate with, or at least receive dreams informed by, the dead.

But just as important in the progress of the show is her family: her husband Joe (essentially, a rocket scientist) and her three daughters.

In the episode of interest, Very Merry Maggie, the dream is of her and her family, represented by dolls. Photographing small objects, such as dolls, is difficult to get right. The use of any form of macro lens induces a very limited depth of field, so focus has to be absolutely perfect. Unfortunately, in this episode, the camera-people didn’t quite pull it off. Some of the doll shots were nicely sharp, while others were quite fuzzy. I doubt that you would notice this on a good old-fashioned CRT TV, but with a Runco VX-2000 projector, with its 1,920 by 1,080 pixel resolution ($AUS36,000), fed from a Strong SRT-5490 high definition TV receiver, with a 1,440 by 1,080 pixel high definition digital TV signal, this difference became obvious.

This (shown to the right) isn’t the only example. Quite often live shots exhibit variable focus sharpness. This is most obvious during dialogue, when the camera is switched between the participants. Sometimes I’ve even noticed the camera focus searching, going a little either side of accuracy, before settling on the right setting.

This is something you don’t see in movies. Looks like TV cinematographers are going to have to work a little harder.

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Talk about slack and lazy!

Posted on March 20, 2007 by Stephen Dawson

No smoking for four hours per day?A couple of people have emailed me, politely I’m happy to report, wondering whether I’m ever again going to add something to this blog. For the past, ugghh!, four months I haven’t felt inspired enough to add anything new here. I’ll try to do better.

In the meantime, the other night I watched a movie on ABC called Green for Danger, a very good little murder mystery set in a war-time hospital in the UK. Well worth checking out, with brilliant dialogue by the Alistair Sims character. My eye happened on a scene set in the patient ward. Notice the sign tacked up on the wall. How times have changed.

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