Monday, March 15, 2010

Again - DRM penalises legitimate users only

Sarah works at Barnet Library on Saturdays and returned very excited this weekend as they've just introduced electronic loan of audio books and eBooks - fantastic you might think. Just download the book to your machine and then portable device and you save a visit to the library. Understandably they want DRM so that it mirrors the same service the library currently offers (you do have to return a physical book or CD after all).
So, Sarah installed the software on the media machine (which has a 10" 800x600 screen in the kitchen for iPlayer/iTunes etc and a second feed to the living room HD TV for Media Centre/Player - two sound cards mean you can be watching an HD recording in the living room and listening to/watching iPlayer in the kitchen). After she'd downloaded a book and tried to play it locally (which is entirely within the allowed behavior);

Quite why you need a hi-res screen for listening to an audio book is another matter. "No matter" I thought - I've got an old iPod kicking about, lets transfer it to that (again, OK in the EULA) and listen to it that way. Click the transfer button and you're in for an eight hour wait while it transcodes the WMA files to AAC. Also - it finds the iPod about one time in five (iTunes sees it every time) and so the chance of it working and you getting more than just a sample of chapters is remote. I did think about pulling out an old Windows Mobile 'phone but at that point I just torrented the book and it's good to go. You try and do the right thing but they make it impossible.

This all begs the question why public money has been spent on this very sub-optimal solution? If you don't want people to listen to these things then don't make them download'able - don't have an audio/eBook service. They will no doubt say that they can't make it easy as people can pirate/pass on the files. However - the OverDrive Media Console allows you to burn regular Red Book audio CDs - so they have NO trouble exposing the data un-DRM'ed! I despair. It reminded me of a time that I bought a couple of episodes of CSI from Channel Five's VOD service - they'd only play on the laptop I downloaded them on and not my media machine connected to the tele. Again - within half an hour I'd scored them off bittorrent (and in HD!)

Thursday, March 11, 2010

JVC monitor calibration software

Whilst at Channel Five recently I got to play with JVC's new monitor calibration software - it's for their DTV-series LCD panels and works using one of those little USB colourimeters (it supports several of the £150-gadget Tottenham Court Road specials). You use a DVI o/p from a PC to feed the monitor and hang the USB detector on the panel and via an RS232-USB connector the software models the monitor and uploads a 1D-LUT that makes the panel conform to a flat D6500 colour-space. Just the job for TV use.
There are a few caveats I can see;

  • The JVC monitors don't switch in a different colour matrix when you go between 601 and 709 working (i.e. SD and HD signal) - the monitor assumes you'll be wanting reliable colour at HD and any SD work is just for content. Previous posts on this here.
  • You calibrate the greys and whites using DVI (hence an RGB source) which only exacerbates my first point.
  • Those little USB gagdets are a couple of hundred quid against a proper colourimetry probe which is a few thousand and a photo-spectrometer which is many thousand. Given how sensitive your eye is (particularly in the blacks) I'm not sure I'd place a lot of faith in something you'd buy in the high street.
  • The software seems to do all it's modeling at 120Cd/m-sq - much hotter than you'd set the monitor for TV use and maybe twice as bright as if you were setting up a film grading display. This isn't as bad as HP's DreamColour range which start at 300Cd/m-sq!
Aside from those quibbles it looked quite good. I like the idea of being able to keep the LUTs for all your monitors and the fact that the software is looking to bring the display into compliance rather than "making it look good"(!)

Tuesday, March 02, 2010

Some more notes on Return Loss

After my poor attempt at an explanation yesterday here is a page from Fluke's manual - much more concise.

Monday, March 01, 2010

Cause of return loss in cat5e cable

One of our biggest suppliers asked us to test a sample of cat5e cable - we tried a couple of different RJ45 ends on the cable - a non-name one and Tyco. We ran the same 1000BaseT test on all six cores for both connector types and if you look you'll see that cores 2 & 4 consistently fail on return loss.
I initially thought it must be down to badly terminated ends but the DTX makes a distinction between return loss over the length of the cable and return loss at the remote end (how on earth it works that put is anyone's guess!) - generic RL is therefore all the reflections along the whole length of the cable that impede the transmitter's ability to send a strong signal.

Now then - it's the brown pair in every case - that suggests that the brown pair is sub spec. We didn't test to an ISO standard (because the cable isn't marked with one) so we used a generic gigabit Ethernet test which is a bit more tolerant.

I have to say I think the cable has a manufacturing fault in the brown pair.

With that in mind we stripped out some of the brown pair from core 2 (bad) and core 5 (good) and you can see the twist in the bad pair is much more variable than the twist ratio in the good pair.

So - it seems like the brown pair in cores 2 and 4 is inconsistently twisted compared to the brown in the other cores.