hifi-writer.com

Well, that was disappointing. This evening I went to see Sherlock Holmes: A Game of Shadows at the local cinema. The movie was okay, but I fear that I failed to enjoy it because I was totally distracted by the horrible picture quality.

Now my local cinema is Limelight at Tuggeranong. This was a new startup a few years ago which took over the closed-down multiplex in the shopping centre, put in digital projectors, gave the place a bit of a brushover, and reopened selling movie tickets at much lower prices.

I’ve been impressed when I’ve been there previously. The black levels haven’t been up to the quality of a modern home theatre projector, but certainly adequate, while colours have been rich and engaging.

So what was going on in Cinema 3 tonight at the 8:20pm showing?

When they were running trailers, I was wishing that they’d turn down the house lights, because they were washing out the picture quite significantly. Then they turned down the house lights as the feature began. I couldn’t believe it. Totally washed out. Colours pallid. Contrast absolutely terrible. I don’t think I’ve seen a picture as low in contrast as this since Panasonic introduced the dynamic iris back around 2003!

I was hoping that perhaps this was something to do with the movie’s prologue, but no it continued throughout the movie. I would have guessed a contrast ratio of maybe 500:1. Not only were the blacks at best a dull grey, the bright parts weren’t especially bright. There’s a scene when some of the characters are chugging across the waters on a clear day in a paddle steamer. Dull, dull, dull!

So instead of being drawn into the picture, I’m wondering how a digital projector can lose contrast. As the lamp reaches the end of its life it dulls, but then the blacks should deepen commensurately.

And there were inconsistencies. When we got to a darker section of the movie, in those scenes where almost everything was dark, then the black levels didn’t actually look too bad. That’s not the behaviour you expect from a projector (or any other display) with a poor contrast ratio, unless it has a particularly aggressive dynamic iris. Which I don’t think cinema projectors have. If light is leaking through the LCD panels or whatever, it becomes even more obvious in dark scenes.

So what was going on?

I had a guess, but waited until the credits started to roll before checking it out so as not to irritate those behind me.

The first few credits of this movie are presented in a fancy script on a lightly coloured screen. When I turned back and looked at the projection booth, this was glowing brightly … on the glass of the booth, through which the projected image must pass.

The ideal glass would capture no part of the light. All would pass through unhindered to the screen for maximum brightness. This glass captured quite a bit of the light. Probably only a couple of per cent of it, to be fair, but the image was clear on the glass. A moment later when the normal scrolling white text on black background credits commenced, the text was obvious on this bit of glass (although, obviously, of quite soft focus).

So here’s my theory: the glass was dirty, and the lamp was dull, perhaps due to nearing the end of its life. I say the lamp was dull because I doubt that the glass — dirty or dusty though it may be — would itself be sufficient to reduce the overall brightness of the image.

But the dirty/dusty glass did, in my theory, far more damage. What it did, I think, was scatter part of the light.

Whenever there was a bright image, there was plenty of light to scatter into the darker objects on the screen (all the men wore dark suits). When there was a dark scene, there was nowhere near as much light being projected through the glass to scatter, so they looked surprisingly good.

So bright scenes looked washed out — including with pallid colours.

So that’s my theory. Next week I shall put that to the cinema proprietors and see what they think.

Now, I’m going to finish watching a movie on a large LCD/LED TV, and marvel at the rich colours and dark blacks.

Do you like Japanese Anime? I have one copy of the Blu-ray for Summer Wars. No box. Ask for it in comments. Australian postal addresses only.

Incidentally, while researching my piece on SACD, I came across a recent study in which double blind tests were conducted to determine whether people could pick between SACDs and DVD Audio discs on the one hand, and the same discs fed through a CD-standard (16/44.1) bottleneck on the other.

They could not. People could not tell the difference:

Claims both published and anecdotal are regularly made for audibly superior sound quality for two-channel audio encoded with longer word lengths and/or at higher sampling rates than the 16-bit/44.1-kHz CD standard. The authors report on a series of double-blind tests comparing the analog output of high-resolution players playing high-resolution recordings with the same signal passed through a 16-bit/44.1-kHz “bottleneck.” The tests were conducted for over a year using different systems and a variety of subjects. The systems included expensive professional monitors and one high-end system with electrostatic loudspeakers and expensive components and cables. The subjects included professional recording engineers, students in a university recording program, and dedicated audiophiles. The test results show that the CD-quality A/D/A loop was undetectable at normal-to-loud listening levels, by any of the subjects, on any of the playback systems. The noise of the CD-quality loop was audible only at very elevated levels.

The article is behind the Audio Engineering Society pay wall, but if you google a key phrase, you should be able to find it somewhere or other.

Now I imagine that there are plenty of criticisms of this study around, picking points of weakness and attempting to invalidate its results. And they may in fact be correct.

But having said that, the best way to overturn these results would be for someone to conduct a scientifically valid study which demonstrates that people can, in fact, notice the differences between formats.

Incidentally, the authors make this observation:

Though our tests failed to substantiate the claimed advantages of high-resolution encoding for two-channel audio, one trend became obvious very quickly and held up throughout our testing: virtually all of the SACD and DVD-A recordings sounded better than most CDs—sometimes much better. Had we not “degraded” the sound to CD quality and blind-tested for audible differences, we would have been tempted to ascribe this sonic superiority to the recording processes used to make them.

Why is this? They suggest — plausibly it seems to me — that the run of the mill CD release has been mixed and EQ’d for adequate performance on a wide range of mediocre equipment, whereas an SACD or DVD Audio has been created in the knowledge that the purchasers will all be careful listeners with respectable equipment, so considerable care is taken in creating the disc.

In short: buy SACD or DVD Audio where possible. It’s likely to sound better than CD, not because of high resolution digital formats, but because the recording has been prepared with love for your own fine system.

Direct Stream Digital (DSD) is the digital format used by Sony in the Super Audio CD (SACD). But SACD is only one form in which it is used. I seem to remember that back in the day, Sony was promoting it as the best digital format for audio archiving. Something about robustness.

Perhaps. But my problem with it is accuracy. Namely, it isn’t very, compared to the alternatives (ie: PCM). Recently I did a piece (should appear early 2012) for Australian HI-FI in which I explain how DSD works (single-bit pulse density modulation: the more 1s, the higher the wave form at that point), and how it terms of resolution it comes in around the same as PCM at 117.6kHz and 24 bits, or 141.12kHz and 20 bits.

But Sony claims a ‘theoretical’ top end of 100kHz, which would imply a bit depth of just 14 bits!

Fortunately, Sony uses noise shaping to move all the quantisation noise up to the HF area were it is less noticable. If you measure the output of an SACD player, you will find that the output of the signal, looked at by frequency, falls away from the audible band up to maybe 25,000 to 30,000 hertz, and then starts to rise again. That rise is the level of HF noise DSD generates.

I measured snippets from the analogue outputs of an SACD player for a few SACDs to illustrate the point. So far as I know, there are no tools to even play an SACD in a computer, let alone extract its digital content for direct analysis.

However I have just been playing with the ‘Immersion’ box set for Pink Floyd’s ‘The Dark Side of the Moon’. One of the six discs contained therein is a Blu-ray which has three different versions of the album: the original 1973 mix in 2/0.0 (all are 24 bit, 96kHz PCM), the 1974 Quad mix in 2/2.0, and the 2003 5.1 mix in 3/2.1.

The 2003 version is clearly the same as the SACD version. So I ripped the audio out of this as six 24 bit, 96kHz PCM files and had a close look at the front left channel. Here is the frequency spectrum for this channel for the entire disc (ie. all ten tracks):

As you can see, this is only shown from around 2kHz. The bottom of the dip — the point at which the ultrasonic noise inherent in DSD overwhelms the signal — is around 32kHz.

Remember, the digital data being analysed here was carried on the disc in PCM format, which has no such problem. This is a DSD issue, and because the final mix was prepared in DSD, it carries through into PCM.

Just to show how inherent this quantisation noise is in DSD, here is the spectrum graph for the three seconds of near silence between the first two cash register ka-chings of the track ‘Money’:

I used different software, obviously, and note that this one is the full spectrum, but with a linear rather than logarithmic X-axis.

Let me stress once again, had the mix been converted from analogue to PCM rather than analogue to DSD, then that rising noise would not have been there.

As for an archival medium, what a dreadful choice!

I had this clever idea, or so I thought, in which I’d test some CDs and compare them to each other. Of course, CDs aren’t comparable — unless they are of the same music. The idea was: when a new digitally remastered CD is released, how does it differ. Suspicious individual that I am, I had half a mind to think that maybe a bit of dynamic range compression was applied in some remasters, with a view to allowing a higher average volume level.

So how to measure dynamic range? I was going to use Cool Edit 2000 which generates some useful statistics about audio files. But one of my editors suggested the Dynamic Range Meter.

The problem with that was the software had expired in August, since the authors had apparently planned to have a better version out by then. It seems that they haven’t.

Fortunately someone else did his own version with a couple of enhancements.

These meters take a pretty naive approach to this. Basically, you take the peak level achieved by the sound file, you take an average measure of the sound file, subtract the latter from the former and you end up with a figure. Express this in decibels and you have a sensible number that you can use to compare versions of music. This figure — the decibels, or DR — is a ratio between peak and average. It would typically range between maybe six and twenty, depending on the type of music.

Now I say this is naive because while the average figure (calculated using RMS methods to overcome the fact that roughly half the samples are negative) should be representative of the file, the peak depends on only one point. If that point is a transient, as it typically would be, there can be a rather large range on its value based purely on fluke. If the sample is on a rising or falling part of transient, then it will be lower than if it happens to be right on the peak. This all hangs solely on when the sample happens to be taken.

But let’s put that aside for the moment. I like to make sure my instruments are working well, and one way of partly confirming this is to compare measurements using two different instruments. So I used the facility in Cool Edit 2000 to gather stats on an audio track and applied the Dynamic Range Meter to the same track.

Oh, oh. Around three to four decibels difference for the RMS Average, with the Dynamic Range Meter giving a lower (closer to zero) value. Consequently its reported dynamic range was also 3-4dB lower than suggested by Cool Edit 2000.

Fortunately Cool Edit 2000 has an export facility, where you can turn an audio file into a text file consisting of a header, and then two long lists of numbers which represent the samples.

I trimmed to test file down to precisely one second in length (for 44,100 samples), exported it to text, imported it into Excel, and did my own max, min and RMS average calculations. This agreed, kind of, with Cool Edit 2000 rather than the Dynamic Range Meter.

(Kind of because Cool Edit seems to call the average, as I calculated it, ‘Total RMS Power’, and gives a slightly different answer — out by up to 0.5dB — for ‘Average RMS Power’).

So am I missing something? Is there a better more representative method for calculating average than I used?

My manual methodology was simple: square each sample, add them all up, divide by the number of samples and take the square root of the result.

Update (6 December 2011): The author of the improved Dynamic Range Meter emailed me back in response to a query and he clarifies things.

It is all to do with reference level. The maximum possible level of a digital sample is 0dB, of course. All other values in the range are negative. If you take the RMS average of a square wave you will get a result of 0dB. That’s because half the samples are at the positive end of the full scale, and half are at the negative end. If you take the RMS average of a sine wave you will get a result of -3.01dB (calculated by 20.log(sin(pi/4))).

Apparently there has been some disagreement over whether 0dB should be take as the reference for RMS measures, or -3.01dB. There are arguments on both sides. Intuitively 0dB seems to be the obvious choice. But as mentioned, that would mean a full-scale sine wave could never get higher than -3.01dB on average.

So in the end, it seems that the international standard has gone for the sine wave reference, treating it as 0dBFS for RMS purposes, which effectively counts the RMS levels of all other signals as 3.01dB higher than they otherwise would have been.

But this does not apply to specific samples. They are still counted with reference to the real 0dBFS. So when you subtract this redefined average RMS level from the peak level, you come up with a result 3.01dB less than the raw numbers would suggest. And in addition, the average RMS level of a square wave is actually positive rather than negative!

According to Wikipedia, the intuitive 0dB = 0dB approach is also the norm for analogue. I’m inclined to think I’ll stick with this, but the less is that it should be made entirely clear precisely how one is doing one’s measurement because there is plenty of room for confusion.

Also by way of apology, the first to ask in comments (Australian postal addresses only) is welcome to have the three Blu-ray disc (discs only, no packaging) set of the National Geographic documentary series ‘Great Migrations’. Four episodes, 200 minutes, 1080i60 video, DTS-HD MA Audio.

(Sorry for the lack of posts lately.)

Lately I’ve been quite startled by the incredibly low prices of a lot of gear. Right now I’m in the process of unpacking a fifty inch Panasonic 3D plasma TV. It’s RRP is an amazing $1,599. That was startling enough, but I noticed in a Good Guys catalogue the other day that it was selling for just $997. I remember very clearly when 50 inch plasma TVs (and these were mere 1,388 x 768 pixels models) finally inched below $10,000!

If you want 3D with this Panasonic, you’ll have to fork out extra for the 3D eyewear, but even so.

Also, I’ve just received word on the pricing of Epson’s new premium projectors — the EH-TW8000 and the EH-TW9000W. $3,599 and $3,999 respectively! Note that the 8000 is, basically, the upgraded EH-TW5500 (it has similar specs), except with 3D support (you get two set of glasses with it). THe 9000W adds WirelessHD.

These are on top of Epson’s other lower cost 3D projectors, released last month. Over the fold is the short article I wrote on that launch for The Canberra Times.
Read more…

Now digital radio in Canberra is usable since, from 5 October, we have finally had a number of ABC stations joining the commercial stations.

Not all the ABC stations, but the ones that are on AM, plus three digital-only stations: ABC Jazz, ABC Grandstand and Triple J Unearthed. Presumably we will also get ABC News Radio, ABC Classic FM and Triple J when we finally move (probably in 2013) beyond the trial phase to a formal implementation of digital radio. The ABC had to choose which to put up in a constrained trial environment (we only have one subchannel — 10B — at the moment, while Sydney, Melbourne and Brisbane have three — 9A, 9B and 9C).

So here are all the channels presently available on digital radio in Canberra, along with the bitrates with which their contents are compressed in AAC+ format:

ABC Jazz, incidentally, is identical to that available on digital TV on Channel 201, except that it runs one second behind on digital radio. Likewise SBS Radio 1 and SBS Radio 2 are on Channels 38 and 39 respectively of digital TV. They both run about 2.3 seconds behind on digital radio.

Comparable? Well SBS on digital TV uses two channel MPEG2 audio at 160kbps, and it’s all talk so to speak. Both the ABC ‘radio’ channels on digital TV — ABC Jazz and ABC Dig — are also delivered with MPEG2 audio, but at 128kbps and, surprisingly, in 1.0 channel format! Yes, I’ve just been switching between ABC Jazz on digital radio and on digital TV, and the former is stereo and the latter mono.

I’m doing a review of Fantasia/2000 for Australian HI-FI and, consequently, exploring the disc. I tend to do this a little more thoroughly than most, so I discovered some extra content.

Some?

A huge amount!

The disc has the following as official bonus content:

• Short film: ‘Destino’ (1080p24 – 7 mins)
• Documentary: ‘Dali & Disney: A Date With Destino’ (480i60 – 82 mins)
• Featurette (1080p24 – 9 mins)

And here are the contents of the orphan files on the disc (ie. files which have no apparent link to them in the playable disc menus):

• 14 Featurettes (480i60 – 144 mins)
• 8 Unused Sequences (480i60 – 38 mins)
• 2 Storyboard Sequences (480i60 – 8 mins)
• 8 Trailers for other movies and products (1080p24 – 9 mins)

Most of those first three categories have real value. The unused sequences for example are such things as ‘The Ride of the Valkyries’ and ‘The Swan of Tuonela’, both of which were storyboarded, but not completed.

It’s weird that these were put on the disc without access. What’s even weirder is their format: almost all the SD content has an average video bitrate (in MPEG4 AVC format) of either 1Mbps or 2Mbps. Particularly with the former, the quality is pretty flaky. It’s almost as though Disney were experimenting with what it could get away with. Virtually all the bitrates were something like 0.997Mbps, or 0.999Mbps. Clearly an output bitrate had been set as a target for the encoder.

Update (12 October 2011): The plot thickens. See the first three comments below. Generally, the bitrate of this extra content (the SD stuff, not the trailers which are far too high) is suitable for streaming or via BD-Live. But not for downloading. BD-Live requires 1GB of storage (although it permits more), and there must be something like 4 or 5 extra gigabytes of SD content on the disc. The single biggest orphan content file is 2GB, although most of them are far smaller.

Now apparently the US version of Fantasia 2000 has a BD-Live feature for accessing the various making-of featurettes (ignore the reviewer’s views at that link regarding the sound quality of Fantasia. He must have been listening to a very, very different version! My views on its weird sound are here.)

Looking at the stats for the US version of the disc, I’d say that it also has all that extra content on it. Although the Australian disc is a little bigger overall (less than ~0.6GB), it has about 2.4GB bigger in its language package, so there is likely at least as much hidden content on the US disc.

So what does the BD-Live do? Download duplicate content? Or merely provide online authorisation of access to the content already on the disc? It’s all very strange.

Not that any of that matters for the Australian version, because it doesn’t have BD-Live.

Update 2 (12 October 2011, 10pm): McCrutchy at Comment 4 below had explored the US disc and found pretty much the same. Tomorrow I shall put a question to Disney, but I’m not hopeful of an informative reply.

Brian Dunning’s usually excellent Skeptoid podcast this week contains a blooper on the subject of burning in equipment. This podcast was a collection of short answers to student questions, one of which was:

Hello Brian, my name is Julian and I am from Malaysia, and my question is: Do burning in headphones improve sound quality?

His answer:

No, burn-in of headphones and other audio equipment is just one more dimension of the snake-oil world of high end audio, akin to super-duper speaker wire. Burn-in is the process of turning on new equipment, sometimes under extreme conditions, to reveal defects. It’s a common, and almost always worthless, tacked-on optional extra by some retailers of electronic equipment. Once in a while burn-in will reveal a defective component, thus saving the customer the trouble of taking the device home to discover it on his own; but as far as burn-in actually improving the performance of consumer electronics, then no, there is no evidence or plausible reasoning behind this.

Obviously I agree with most of this, but there are two problems. First, Brian seems to misunderstand what ‘burn in’ means conventionally amongst audiophiles. It is not to expose defects. Indeed, it isn’t even to push equipment hard. It is running the equipment normally for some hours, or more typically, tens of hours. Some audiophiles claim that this improves the sound of the equipment.

The second error he makes is in equating the equipment about which the question was asked — headphones — with electronic equipment. These are very different beasts. Headphones are, like loudspeakers, electro-mechanical devices. They convert electrical energy into acoustical energy (which is simply mechanical energy in the form of compression waves in air). They do this by using a linear electric motor to push a cone or diaphragm of some kind. This is designed to be extremely stiff in the frequency range of operation, but nothing is perfect and to some degree or other it flexes. This cone or diaphragm is supported by a suspension system, called a ‘spider’ in the case of a loudspeaker. This is often a stiff fabric rendered springy by means of concertina folding. The edge of the cone or diaphragm is typically also surrounded by some material in order to locate it in space. In speakers this is usually either some kind of foam, or a soft rubber.

All these moving bits change their state with use. The assumption is that they are stiff to begin with and loosen up with use, and this seems to make sense. The assumption also seems to be that they loosen up from their initial stiff state to a normal operational state fairly quickly — say, within dozens of hours of use — and maintain this state for a long time. Think of a tipped over ‘S’ curve.

Whether or not this has any perceptible effect on sound I do not know because I have never done a test. The procedure for such a test would be easy enough. Take two sets of same-model loudspeakers. Use a panel of listeners of sufficient variety and number to generate statistically valid results. Have them listen to both sets of speakers new out of the box, but only briefly, and score any differences in sound.

Run one of the sets of speakers extensively for a lengthy period to burn them in. Get the listening panel back and, double blinded, compare the barely-used and heavily-used speakers again. Score any differences in sound. If this second score is significantly greater than the first score, then the existence of an audible effect would have been established.

Some people swear that burn-in does make a difference in their experience. I suggest that it’s almost impossible to tell without some formal protocol as outlined. You cannot compare the sound of a device from one day to the next in the way that most people do these things. All you can do is compare the sound of a device with your memory of how it previously sounded, and I’d strongly suggest that you shouldn’t trust such a comparison.

But that doesn’t take away from the fact that it is almost certain some physical changes do take place in loudspeakers (and headphones) when they are run.

Electronics? Cables? No way.