A Note On Playing Back Commercially-Recorded Blu-rays

Just as it was with DVDs, when movies first started to be distributed in that format, commercially-recorded Blu-ray disks today use an encryption system, which is sometimes referred to as ‘content scrambling’, to prevent people from making unauthorized copies. It’s actually named ‘aacs’.

Experts already know about this, but I’m putting this in layman’s terms for anybody who might not.

Basically, Blu-ray playback-devices have a hidden store of public keys, which the users are not allowed to access, and this time, the company is able to update that store of keys via the Internet, because most Blu-ray players today are also online devices.

Unlike how it is with Blu-rays, the content-scrambling system of DVDs was famously hacked. This means that Linux computers are well-able to play back Movie-DVDs. OTOH, the ability to play back commercial Blu-rays, is mainly unsuccessful on Linux computers, or on any other unauthorized devices, because the content-scrambling which gets used – was never hacked. As long as the encryption continues to work, Linux users and pirates will not be able to play back or rip Blu-rays.

As it stands, the company is able to revoke public keys which it was once using.

This is a shame, because some Linux users might only be wanting to view Blu-ray movies which they purchased and paid for. But the main fear of the industry remains, that as a platform, a Linux computer is more susceptible to an unauthorized copy being made of anything, which that Linux computer would also be able to perform authorized playback of.

Therefore, when I gave instructions on how people can record Blu-rays privately, my assumption was that we would not be using any encryption. I don’t see encryption as being important in any way, for home-movies which people might shoot. But, the Blu-ray folder must nevertheless contain a sub-folder named ‘CERTIFICATES’. In the example I wrote about, this sub-folder will simply remain empty.

Further, the mere use of the Blu-ray (single-layer) disk, as a step-up from DVD+Rs, where a Blu-ray can store up to 25GB of pure data instead of 4.7GB, is unfettered for Linux users to use as they wish. All we need is an external Blu-ray burner, and we’re all set to burn pure data. But as soon as we want to burn something using ‘UDF’, which is the approved file-system of Blu-ray players, the level of difficulty already increases, even though no encryption has been used yet.

(Updated 09/19/2017 : )

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How To Burn Blu-ray Movies using Linux – via the GUI

One project which I had half-installed on my laptop named ‘Klystron’ some time ago, but which was not working, was software that would make the task straightforward to carry out, to burn Blu-ray movies from a Linux computer. Because I finally wanted to get that working, I spent time on this in-depth today.

One fact which many people understand, but few people know how to manage, is that Blu-ray movies are not supposed to be burned using the ISO9660 File-System, nor, with the .ISO-Files typically associated with that FS, that store its images. Technically, Blu-ray movies are supposed to be burned using a File-System called ‘UDF’, and version 2.50 of that preferably. Under certain circumstances, v2.01 of UDF may have to suffice, since Linux support for v2.50 is still lagging.

I will spare the reader a lengthy account of what did not work. In order for this to work, I needed to have the Debian Multimedia Repository installed in my /etc/apt/sources.list , which should be straightforward for other people to duplicate. And my main purpose in having this repository, was to get the package ‘tsmuxergui’, version 2.6.11 . In addition, I was working with ‘K3b’ , v2.0.2 .

tsmuxer_1

‘tsmuxergui’ is a GUI-front-end for ‘tsMuxer’, which is a program that can be used to set up Chapters and other playback details, as well as the 1920×1080, H.264-compressed video files of course, that are supposed to make up the program on the final Blu-ray.

tsmuxer_2

As my burner, I used the external ‘Pioneer BDR-XD05′, that connects via USB 3.

There is one additional component which I needed, before K3b was willing and able to burn the UDF File System required, which it is not able to do out-of-the-box:

An out-of-tree version of ‘cdrecord’ , v3.02a7

According to its authors, the versions of cdrecord that have been placed in the standard repositories belongs to ‘cdrkit’, not ‘cdrtools’, and cdrkit fails to provide the back-end, which K3b would need to burn UDF. Yet, to try to perform a binary install of the out-of-tree version, would have been very dangerous to my system. So what I did, and what I would urge other people to do, is to use one of the source-code (tarballs) from above.

First, if the reader has ‘wodim’ installed from the package-manager, I would recommend uninstalling that, just to make sure that package-version-binaries are not overwritten by the out-of-tree versions. Then, I used the above source-code, to custom-compile ‘cdrtools’.

The nice feature about this version, is that it does not even install itself to ‘/usr/local/bin’. Instead, it installs its binaries to ‘/opt/schily/bin’ , when we finally give the command ‘make install’ with root privileges, so that the ultimate risk of messing up the system is small.

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Some Speculation About Practical Phosphors

In theory, the way fluorescent light-bulbs work, is that they already have a light-source of shorter wavelength – and therefore of higher photon-energy – to excite a phosphor, the latter of which emits a pleasant mixture of wavelengths of light – in general, longer wavelengths than that of the energy-source; any mixture of phosphors will do. The light source is allowed to be a Blue LED, rather than a UV light-source.

What I discover in practice, is that the choice of phosphors manufacturers can work with is rather limited. For LED-Light-Bulbs that are stated to produce a color-temperature of 2700K, they tend to use “Y3Al5O12Ce”. Additionally, I have discovered the availability of a newer type of light-bulb, as shown in this photo:

foxy_150409180629

In which a higher voltage is applied directly to an Electroluminescent material.

What strikes me as both convenient and remarkable about these light-bulb-types, is that The color matches very closely. What this observation would seem to suggest, is that the EL material used in the newer light-bulb-type is a hard crystal, that matches the composition of the phosphors used in the LEDs, mentioned above. Additionally, this would seem to suggest, that the layer of the phosphors used in the LED-Light-Bulbs described as having 2700K color, is rather thick, so that very little of the Blue LED’s light passes through, since the light produced via EL has no Blue LED to modify its color-quality.

I suppose then, that the manufacturers have simply added another substance to this phosphor – in small quantities – that causes it to become conductive.

Dirk

 

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I could make a loose inference, about what Lumens are.

In the later part of my childhood – in the 1970s and 1980s – we had incandescent light-bulbs, and we knew that only a small part of the so-called light they emitted was in the visible part of the spectrum. We often used this light-bulb type, because we had no better alternative. We knew that the visible part of the emitted light might have been 15% or 10% of the consumed energy.

Granted, in Industrial or Commercial Lighting, there existed other types of fixtures, such as mercury-gas-discharge tubes, that excited a phosphor with ultraviolet light, so that the phosphor was made to fluoresce. Or in some cases simply – a gas-discharge tube, with a gas-mixture of a composition unknown to me.

But, when I go to buy light-bulbs today, as an adult, like all the other customers, I see Compact Fluorescent Light-Bulbs, as well as LEDs, the brightness of which is stated in Lumens. What I generally tend to find, is that light-bulbs of the fluorescent family, which are meant to be equivalent to the ~Old, 100W~ incandescents, tend to draw approximately 23W, and are stated on the packaging to produce about 1500 Lumens.

Lightbulbs of the LED family with the same equivalence, are stated to draw about 16W, and to produce about 1500 Lumens. I have actually found LEDs, which are stated to draw about 17W, and to produce 1600 Lumens of visible brightness, but which possess a visibly-larger base, from the other types.

If I could just hazard a guess, I’d say that one way to understand Lumens, is to start with the Watts of light in the visible part of the spectrum, and to multiply those by 100. What this would suggest, is that the most-efficient LEDs waste about 1W as heat, while then fluorescents still tend to waste a bit more energy, such as perhaps 8W – some of that in the form of UV light, making those approximately 65% efficient. But this would also mean, that the efficiency of modern LEDs is hard to improve upon. If the brightest variety only seem to produce 1W of waste heat, out of 16W or 17W consumed, it would make most sense to infer that in that range of efficiencies, the Wattage can be translated into Lumens quite easily. More Watts will simply produce more light, and fewer Watts will produce less light. In percentages, the LEDs would seem to have an efficiency of about 94%.

If we have a new light-bulb type, that draws 4.5W, but that produces visible light amounting to 350 Lumens, it would follow from this thinking, that this type is wasting about 1W / 4.5W. In percentages, this would imply an efficiency of 78%.

I suppose that I can offer a comment on the temperatures which the light-bulb-bases of household LEDs reach…

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