Home Entertainment Blog Archive
Brought to you by your friendly, opinionated, Home Entertainment and Technology writer, Stephen DawsonHere I report, discuss, whinge or argue on matters related to high fidelity, home entertainment equipment and the discs and signals that feed them. Since this Blog is hand-coded (I like TextPad), there are no comments facilities. But feel free to email me at scdawson [at] hifi-writer.com. I will try to respond, either personally or by posting here emails I consider of interest. I shall assume that emails sent to me here can be freely posted by me unless you state otherwise.
This archive is for an uncertain period commencing Thursday, 29 April 2004
Some companies send me DVDs, and occasionally they send me duplicate copies. Or, from time to time I decide to get rid of some discs that I think I'm unlikely to ever watch. So, to reward some loyal readers, I thought I might give away some from time to time.
So, to start this rolling, I have the four DVD set of Joss Whedon's TV Series Firefly (which, I notice, someone on IMDB has called 'The worst show of all time next to The O.C.').
I would prefer the giveaway to be to someone here in Canberra, who can drop around and pick it up, since I don't particularly want to be out of pocket for postage.
Note, the discs are prominently stamped 'Sample disc, Region 4, Not For Sale', and don't have covers, so don't apply unless you're really a fan or can give them to someone who is a fan, and won't mind the lack of covers. Write to me at scdawson (a) hifi-writer.com if you're interested.
Whenever I'm writing a short piece on consumer DVD recorders, I have to pick and choose what I will actually talk about. That means leaving out some of the things I consider are probably of less importance to the target readership.
So, for example, when I write about the differences between DVD+R and DVD-R (things are a bit more complicated with the RW versions), I usually write something like: 'For consumer recorders, there are no particular advantages either way between DVD+R and DVD-R. Just make sure that you get the right one for whichever recorder you choose.'
But, of course, there are differences. Note that here I am talking only about consumer recorder use, not computer DVD burner use.
A minor one is that DVD+R uses the +VR format, whereas DVD-R sticks with the Video format (the same as that used by purchased DVDs). Now the +VR format is highly compatible with DVD players. Indeed, I've never had one not work. But it is still rather strange. For example, a duly finalised DVD+R has more Titles on it than you'd expect. Let's say you record four programs, each in its own Title and each, therefore, with its own menu entry. But the DVD+R will hold not four, but ten titles. Titles One through Four will be those four Titles linked to by the menu entries. Title Five will be the main menu itself. Titles Six through Ten will be repeats of the first five Titles, although they often work unreliably. I can't quite fathom why this would be. (The Titles are repeated, not the data. Titles can link to any data so the existence of a logical Title does not, in itself, ensure that there is additional data.)
I also find that DVD Bit Rate Viewer 1.4 just won't recognise any Titles on a DVD+R. Or, rather, it recognises them but considers them all to have a duration of zero seconds.
However my major beef with DVD+R is that it won't support a 16:9 aspect ratio. If you record an anamorphic widescreen program from, say, a digital set top box, the recorder sets a flag of 4:3. This isn't a problem for those using widescreen displays because you can force a 4:3 program to display in widescreen. But for those who have a 4:3 display, there is no way that they can trick the DVD player to reformat the picture into letterboxed widescreen, so the result will always be distorted.
Since I outlined my measurement methodology in the entry below, here are some recent results found using that methodology (1kHz output only reported).
| Model | Specification | Power output per channel (1kHz continuous) | |||
|---|---|---|---|---|---|
| 7 | 5 | 2 | 1 | ||
| Denon AVC-11SR | 7 x 125 | 62 | 127 | 156 | 167 |
| Harman Kardon AVR-8500 | 5 x 110 | - | 132 | 159 | 176 |
| Integra DTR-7.4 | 7 x 100 | 93 | 102 | 134 | 148 |
| Integra DTR-8.4 | 7 x 110 | 99 | 116 | 144 | 163 |
| Marantz SR-7400 | 7 x 105 | 82 | 93 | 133 | 152 |
| Rotel RSX-1067 | 7 x 100 | 118 | 127 | 151 | 158 |
| Sony STR-DA5000ES | 7 x 170 | * | 113 | 203 | 209 |
| Sony TA-DA9000ES | 7 x 200 | 134 | 157 | 192 | 192 |
| Yamaha RX-Z9 | 7 x 170 | 123 | 150 | 168 | 182 |
| * The protection circuitry in the Sony STR-DA5000ES receiver operated too aggressively for me to obtain valid results with all seven channels running. | |||||
From the above, it's clear to see that different brands have different philosophies when it comes to specifying output. Harman Kardon and Rotel are very conservative, and their outputs actually exceed specification with all the channels operating at the same time.
Some kind of standard would be useful here because, the way it is, it's impossible to compare the quoted specification between brands.
ADDENDUM (Tuesday, 10 August 2004, 10:36 am): I should have made a couple of other points. First, we use 240 volt power here in Australia, so these measurements might not be valid in places like the United States, where 110 volt power is used since, necessarily, similar receivers will use either different transformers, or different windings on the same transformers.
Second, take all my measurements to have an error range of about plus or minus five per cent. The load resistors themselves are only rated to 1% accuracy. The meter is probably less accurate than that, and I have to find the point just before clipping by eye on an oscilliscope. In addition, to derive the power output I have to square the measured RMS voltage, which amplifies considerably any measurement error.
Finally, don't get too het up about precise power measurements. The difference between 100 and 105 watts is a mere 0.2 decibels!
A reader, Tony, suggested a couple of months ago, that I write an article on 'The Steve Dawson method of testing Receivers'. I don't think it's worth an article as such, but I would like to outline my process, and why I do it.
My technical tests are rather basic. Wire up five, six or seven, as appropriate, eight ohm resistive loads (Dale NH-250 load resistors, 250 watts capacity each, 1% tolerance) to the speaker terminals of the receiver. Plug a sine wave generator into the 5.1, 6.1 or 7.1 channel inputs (if possible, otherwise plug into stereo inputs and select 5, 6 or 7 channel 'stereo' mode). Put oscilliscope probes onto one of the loads, and RMS voltmeter likewise. Turn up the input signal until signal starts to clip, then turn it down a touch until the signal is perfectly clean (to the eye). Read voltmeter. Power equals V^2/8.
Do this for 100, 1,000 and 20,000 hertz. Do this for seven channels, five channels, two channels and one channel.
Clearly this isn't a 'real world' test. There's no such thing, unfortunately. The lack of reality is reflected by the following:
- loudspeakers are not resistive loads, but reactive ones -- however the characteristics of their reactance varies with each speaker so there can be no widely applicable realistic test;
- receivers are never called upon to produce a continuous high level sine wave (except by people like me); and
- receivers are virtually never called upon to produce maximum power from all channels at once.
A better test would be to choose some representative DVD sound track. Say one that works all the channels heavily. Record the pre-amp output and the speaker output and compare. Advance to volume to a point just below significant differences (ie. distortion) becoming evident. Report the average and peak output levels from all the channels. But this would involve many hours of trial and error, and still would not be truly representative (for example, since bass is higher in level than the midrange and treble, a receiver driving a sub/sat system will have an easier time of it than one driving five or seven full range speakers). I may experiment along these lines some day.
Still, I do these measurements simply because the results they deliver are a useful proxy for overall quality and performance. Just like the weight of a receiver is a useful proxy. These things say something about the care that a manufacturer has put into the receiver.
Andrew, from Canberra, writes to me:
I refer to your article on the Hitachi DZ-MV580E video camera.I wrote back to him:I always like to read the Techno write-ups featured in The Guide [in the Canberra Times] each week. I think they are very worthwhile.
However, I was a little concerned with a misleading paragraph which talks about MPEG2, i.e.
'Instead of the DV format used on tape-based cameras, this Hitachi model uses the higher quality MPEG2 format used on DVDs.'
I would hate the general public to pick up on this statement. It is very misleading. I think the public should be made aware of the facts about MPEG2 as used on DVDs. Basically, MPEG2 is a compressed format which throws away data and image quality so that the video files will fit on a DVD. Although MPEG2 compression remains very high quality, it is a delivery format and not an editing format. It is inferior to the DV format used on tape-based cameras because of the higher compression and amount of image data discarded and the difficulties in editing MPEG recorded material.
You probably know all this already, but readers will certainly be misled if they are told otherwise.
Thanks for your thoughts on this. I agree with you completely that DV is much better for editing, if only because it can be cut accurately at a precise frame without having to be re-encoded. This is a big weakness with MPEG2 but, as you say, MPEG2 was never intended as an editing format. It's really only the convenience of optical disc media that has forced MPEG2 into this mould -- via DVD cameras and consumer-level DVD recorders.Only on re-reading this did I notice that Andrew's note could possibly be misinterpreted to suggest that there is no compression in DV. In fact there is, to a ratio of around 5:1.Anyway, you have prompted me to learn more about DV (digital video cameras aren't actually my speciality, but after the reading I've just done they are starting to come into, er, focus.) I suspect that my throw-away adjective -- 'higher quality' -- was in appropriate.
Is DV better quality than MPEG2 (as implemented on DVD), or vice versa?
On the face of it, DV seems better. A fixed video data rate of 25Mbps for DV, vs a variable data of typically between 4 and 7Mbps, with an absolute top limit of 10Mbps, for DVD. Did I mention in the review that at the 'standard quality' recording setting, the Hitachi video camera used a fixed bit rate of 5.24Mbps? It saves quite a bit of space, compared with DV, by recording the audio in MPEG format at around 230kbps, rather than the much bulkier PCM used by DV.
Anyway, that's one strike in favour of DV. But we have to look at the reason why DV uses such a high video bit rate. First, because of the technology available at the time of its development (1994), and the need to perform the compression in real-time, the compression algorithms were kept relatively simple. Just consider the difference in computing power between, say, a 1994 notebook computer and a 2004 one, as a kind of proxy for the amount of processing that could be done. The notebook I purchased in 1994 had a 80486SX processor running at 25MHz. If I were buying a new notebook computer today, it would probably have a Pentium 4 running at 3,000MHz!
At the time of its development for DVD implementation, there were no particular worries with allowing the compression algorithm to run many minutes for each minute of actual video. It was only later (with DVD recorders) that real-time compression became important. MPEG2 also uses variable bit rates so it can optimise bit allocation to the parts of the video that most need it. DV, designed for fixed speed tape, did not have this dodge available to it. A black section within a video uses as much data as a highly detailed action sequence.
The very drawback of MPEG2 when it comes to editing -- the IBP compression system in which just one out of twelve or fifteen frames is held in whole, while the rest are derived from difference information -- also makes for a considerably more efficient compression technique (which, of course, was why it was developed). Clearly DV can never suffer from artefacts evident on poorly encoded DVDs, such as human faces appearing to morph in playback because of insufficiently fine capture of subtle movements. But, then, well encoded DVDs don't suffer from this either. (I must think of a catchy name for this under-reported artefact).
I suspect that when it all comes down to it, DVD-style MPEG2 and DV are of roughly similar recording quality, although DV is clearly better for editing.
I shall copy your email and this response to my -- until now -- sadly neglected Blog. I shall also try to squeeze in a note in a forthcoming Canberra Times review, recanting my position.
I have no excuse. Just been variously busy, lazy and in shock. This last came from ballooning excess bandwidth charges. My hosting contract included 500MB per month. In recent months bandwidth has been between 1.5 and 2GB! My $38 per month cost was suddenly $115 or $120.
Anyway, new times, new contracts. The new one has a bandwidth limit of 2GB per month (and a stack more storage). But if bandwidth blows out again, I shall have to consider going offshore to a cheaper hosting service. Any recommendations? Reliability of service is very important to me.
The humble CD, originally meant to be just a simple carrier of digital audio on a spiral track, has been finding more and more uses. First as a carrier of data and programs for computers, then as a recordable device. Various ways were found to stuff video onto it (VCD and SVCD) and subsequently the concept was expanded to increase the density of data storage into a system now known as the DVD.
But this use as a blood testing device seems to be in a completely different category.
Elsewhere I have been pondering on how government rules produce interesting workarounds. I was using the software product AnyDVD from SlySoft Inc as my angle into this, and it occurs to me I ought to mention the product here as well.
My ponderings were about the essential illegality of this product, given that it decrypts content-protected DVDs, which breaches such laws as the Digital Millennium Act in the United States and similar legislation here in Australia. The main reason I purchased it was to overcome Region Code restrictions on my computer's DVD drive, and secondarily to eliminate User Operation Prohibitions.
And it does all this very nicely, without being in any way noticable. As it happens, it has decrypted a dozen or so DVDs very nicely as well, entirely quietly and in the background, with no noticable lag. Costs $US39.
Last Friday's Bleat
by James Lileks records his observations on receiving high definition TV. Nice piece, as usual, but some technical corrections are in order. He says:
Normal TV has something like 440 lines on the screen. (Or 380. Or 400. Cursory google search leads me to baffling videophile sites I haven't the patience to wade through.) DVDs have about 800 lines. (See parenthetical note to previous sentence.) They're better. HDTV has 1081 lines.
I suspect that there is a widespread confusion about TV resolution because this has always been measured in terms of 'lines'. But there are at least two kinds of lines on a TV screen: horizontal ones and vertical ones. The number of discernible horizontal lines of resolution equates to the vertical resolution in
pixels; and the number of discernible vertical lines is the horizontal resolution in pixels. So here's a primer on what resolution you can expect from various signals:
| Name |
Horizontal resolution
(number of vertical lines able to be visually distinguished across the width of the display) | Vertical resolution |
| US Analogue TV (NTSC) | ~400 | 480 |
| Australian (and European and Indian) Analogue TV (PAL) | ~400 | 576 |
| US VHS VCR | ~200-250 | 480 |
| Australian (etc) VHS VCR | ~200-250 | 480 |
| US DVD with analogue connection | ~500-550 | 480 |
| Australian (etc) DVD with analogue connection | ~500-550 | 576 |
| US DVD with digital (DVI/HDMI) connection | 720 | 480 |
| Australian (etc) DVD with digital (DVI/HDMI) connection | 720 | 576 |
| High definition TV (US and Australian) | 1,280 | 720 |
| High definition TV (US and Australian) | 1,920 | 1,080 |
In the case of the HD signals, the actual visible resolution depends largely on the display device. There are few, if any, devices available yet that actually support all 1,920 horizontal pixels, even if they can pull off the 1,080 vertical pixels. This will change soon, though.
In the middle of last year
I pointed out a major deficiency in the mastering of the Australian PAL version of
Independence Day. Namely, for the bulk of the movie, most of the video frames are constituted by fields from adjacent film frames, producing severe interlacing problems in some setups.
Happily, a new double-disc release of this movie will be appearing in Australia shortly, eliminating this problem. The graphic here shows a frame detail from the original, and the same frame detail from the new release.
Other differences:
- the new version is Region 4 only, while the previous one was Regions 2 and 4. Does this mean that Europeans are stuck with the old one?
- the old version used seamless branching to provide both the original theatrical version and the extended version (which adds about eight minutes), the new release is the extended version only (147 minutes).
- the old version had a couple of commentaries (one for each version of the movie) and a Dolby Digital 5.1 sound track at 384kb/s. The new version has one commentary, the DD 5.1 track is at 448kb/s and a 768kb/s DTS track is also provided.
- the average video bit rate is a little lower in the new version: 4.9Mbps vs 5.33Mbps on one measure, 4.85Mbps vs 5.41Mbps on another.
Excellent analyses -- a little old (by several months, that is, rather than years) -- of the US movie industry, how to estimate whether a movie has made money, and how what is happening now will affect what we'll see in a couple of years. Go here first, then here for the followup.