Tuesday, March 29, 2011

Video post production a 'dying industry' - yikes!

This is a table nicked from the Wall Street Journal (via my pal Hugh - @hugh_waters on Twitter). On one hand it's very worrying but on the other hand it's what I've suspected.

  1. The equipment required for TV post production is now a £1.5k laptop and not a room that cost a million quid to install (twenty years ago). It's why audio still makes money (you still need an expensive room even thought the equipment is cheap) and why OBs, studios etc will always be profitable.
  2. Post production is largely run by owner-operators; folks who have an emotional attachment to it and will do work at a loss for the love of it and have a far too optimistic view of the future.
I don't know what the answer is - I'm going to try and concentrate on designing/building audio suites, TV studios etc and avoid edit rooms!

Monday, March 21, 2011

Side channel attacks with encrypted data

In cryptography, a side channel attack is any attack based on information gained from the physical implementation of a cryptosystem, rather than brute force or theoretical weaknesses in the algorithms. For example, timing information, power consumption, electromagnetic leaks or even sound can provide an extra source of information which can be exploited to break the system.

Several examples that I think are interesting are;
  • Secure web applications; Bruce Schneier's excellent blog (which is required reading if you have any interest in security/crypto) describes the attack carried out on the IRS's (what they call the Inland Revenue in the US) online tax form site;
    ...it leaks a fairly accurate estimate of your Adjusted Gross Income (AGI). This happens because the exact set of questions you have to answer, and the exact data tables used in tax preparation, will vary based on your AGI. To give one example, there is a particular interaction relating to a possible student loan interest calculation, that only happens if your AGI is between $115,000 and $145,000 -- so that the presence or absence of the distinctively-sized message exchange relating to that calculation tells an eavesdropper whether your AGI is between $115,000 and $145,000. By assembling a set of clues like this, an eavesdropper can get a good fix on your AGI, plus information about your family status, and so on.
  • Compromise of HDCP; The encryption used over HDMI displays is industrial strength and cannot be broken by brute force methods (not in this universe, anyway!) - instead by freezing the memory used by a software BluRay player you can be assured that the volume-key is somewhere in memory. By stepping through 128-bits at a time and having a try at decrypting the first few frames of video (which are very clear when they are decrypted) you quickly find the key for that BluRay or HD-DVD disk.
  • The use of 'cribs' when decrypting Enigma traffic; Bletchley Park had typically less than a day to decrypt most traffic captured from German wireless telegraphy as they changed the rotor-positions in the Enigma machines every twenty-four hours. Apparently the intelligence gained by the French who were experts at recognizing the morse-key style of German operators (and hence were able to track which army group Fritz or Herman worked for) along with a knowledge the ten most profane German swear words and ten most common German girl's names meant they code-breakers had a head-start with seed-words which cut down the key-space to a manageable size that was process-able by 1942 mechanical computers!

Interesting though these examples are, the one that really peaked my fancy this week was the side-channel attach described by the Associated for Computing Machinery on the encryption used in VOIP systems. It turns out that most VOIP systems (Skype included) use variable-bitrate compression ahead of the encryption process (typ. AES at 128-bits). It turns out that by training a Markov Model with the encrypted data (yet knowing what the words spoken were) you can subsequently get around 50% accuracy with data streams from unknown talkers. Given that English has a lot of redundancy you could glean most of what was being said!

Read all about it here.

Thursday, March 17, 2011

Blackmagic, have the courage of your convictions!

I've often bad-mouthed Blackmagic as they often build to price rather than spec. In the past when I've complained about their interpretation of the SDi spec they've always said that so long as they can light-up a monitor they're 'democratizing digital video' or some such(!) Anyhow - Joel showed me that they are now featuring screen-grabs from a Tek rasteriser on their website; they weren't so keen on it five years ago!

Saturday, March 12, 2011

People's expense accounts depend on their unquantifiable skills!

In 1999 the Super Audio CD format was released - higher sampling rate and longer word-length than the venerable 44.1Khz/16-bit Red Book standard that traces it lineage back to the late seventies and the Sony F1 digital audio system.
I've spoken to audio engineers who have made a very good career out of there being a benefit in re-mastering recordings to this newer standard. Their contention is that the difference is "night and day" (please go back and read that post).
Anyway - in 2007 a couple of chaps from the AES did a double-blind test to see if audio professionals could tell the difference - it turns out they can do no better than random. Remember - that was audio engineers, dubbing mixers, and other people who know what to listen for in properly recorded audio. Mix Magazine did a very good write-up under the title of The Emperor's New Sampling Rate!

This all reminded me of a project I was involved in at Oasis TV in the late nineties where we were home-brewing an audio-FX server for the dubbing suites. At the time 9 gigabyte SCSI drives were £1,500 and so compression was implied! None of the dubbing mixers liked this idea and so I made up a CD of various recordings; spot-effects, different music styles, dry vocal recordings and finished mixed programme. The compression we were using was MP2 (so not as good as the now-ubiquitous MP3) at 128, 164, and 192 kBits per sec (as well as uncompressed).
Remember - these were the golden-ears listening on £10k matched amp/speaker combos. It turns out that somewhere between 164 and 192kBits per sec these guys dropped to about 50% accuracy in discerning the compressed audio from the original.
Actually I think it's a bit more complicated than what these two double-blind tests suggest; I store all my music at 192kbit MP3 encoded using LAME 3.9 - for 99% of my music I can't hear the difference. However;
  • On some passages (typ. splash cymbals and some acoustic guitar parts) I am aware of compression artefact's.
  • An old VT editor once told me (around fifteen years ago) that although he liked the look of (the then new) DV format he felt more tired after a day of editing DV footage compared to BetaSP - the differences aren't immediately clear but over time one is better (in some way?) than the other.

I do believe that you can only get to the truth of these things by statistical analysis - I place no faith in audio professionals who expect their view to be taken seriously without the numbers to back it up. Their salaries depend on them being able to 'hear' the differences - if they are there or not.

Friday, March 11, 2011


I've been following the Stuxnet worm in the technical press and it is fair to say that this is probably the world's first weaponised computer worm. In a very real sense this is cyberwar.
From Bruce Schneier's excellent blog;
Stuxnet was expensive to create. Estimates are that it took 8 to 10 people six months to write. There's also the lab setup--surely any organization that goes to all this trouble would test the thing before releasing it--and the intelligence gathering to know exactly how to target it. Additionally, zero-day exploits are valuable. They're hard to find, and they can only be used once. Whoever wrote Stuxnet was willing to spend a lot of money to ensure that whatever job it was intended to do would be done.

Symantec's report is very thorough but somewhat long!
The best expose on the whole subject is Steve Gibson's podcast on the subject;

Tuesday, March 01, 2011

Tony Drummond-Murray presents...!

This talk will start with the early methods of TV recording using film (Telerecording) and will briefly touch on some of the problems associated with TV cameras of this era. From there it will move on to Videotape recording (VTR), and will be illustrated with a few historical slides showing the early equipment. "VTR" is a vast field in this context, covering Recording, Playback, Editing (physical cutting and electronic splicing), Transverse and Helical scan tape formats, slow-motion and freeze-frame, and so on....

I've known Tony for many years, he is a great guy and a good speaker. We have staff meeting that night so I'll miss this unfortunately.