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Thousands and Thousands of Hours of PVR TV
Thomas Hawk writes "Cory Doctorow is posting over at Boing Boing about some technology that he apparently saw this weekend at London's Open Tech conference. According to Cory, this new technology from Promise TV takes the form of a home-built PVR with lots of high-capacity hard drives and claims to be able to record every show on every channel being recorded in the UK for an entire month. 'Why program a TiVo to get certain shows for you when you can record every single show on the air, all at once, and then use recommendations, search, a grid, or any other means you care to name to figure out which of those thousands and thousands and thousands of hours of programming you want to watch.' The company seems somewhat cryptic with a simple website that appears to be collecting your email addresses for an announcement in August. "
30 actually:
http://freeview.co.uk/whatson/index.html
I doubt you'd bother making something that recorded from an analogue source - too much CPU power.
well, with my PVR machine I record at 9Mbps for video and 384Kbps for audio, barely over 1MB/s. With two tuners, that's just over 2MB/s. Watching one of the previous recordings while recording two shows at the same time, that's just over 3MB/s. Even a mediocre HD can handle that no problem. Hell, while it's doing that it's also either scanning a show for commercial breaks or recompressing that 4GB/hour mpeg2 stream to a 1GB/hour mpeg4 stream, so there's a bit more workload, still doesn't break a sweat. So, one HD per recording is way overkill.
I seriously doubt they'd be able to record everything out there.
I mean, just look at a standard Tivo box. 40G hard drive gives you about 35 hours of recording time. And that is just one or two shows at a time.
A month's programming on 200 channels simultaneously?
c'mon.
The version of show recorded 5 main channels, plus a couple of digital channels, such as CBeebies.
:)
The machine _was_ as simple as you think: a few grands worth of discs, one TV card per channel (with hardware encoding), and some reasonable hardware.
The control interface was custom.
(yes, I saw it on Sunday
It would be relatively easy to record all the Freeview channels at once. You only need one receiver per multiplex, not per channel, then you just record the raw data stream which contains all the channels on that multiplex. IIRC there are only about half a dozen multiplexes. So 6 tuners would be enough to record everything on Freeview.
As this sounds like pure marketing, we can make some assumptions:
a) Number of channels included will be the minimum available to all.
b) It'll be "VHS quality" recording.
There are 5 terrestial TV channels in UK:
BBC1
BBC2
ITV (commercial)
Channel 4 (commercial)
Channel 5 (commercial)
We've about 50 via digital TV, and loads more via cable or satellite.
However there are only 5 available right now.
So, that's 5 channels * 24hrs * 28 days = 3360 hours of recording.
Lets assume a VCD bitrate of 1300kbit/s video 128kbit/s. Total 1428kbit/s.
Number of seconds in 3360 hours
= (3360*60)*60
= 12,096,000
So, for all that video we'll need
= 1428 * 12,096,000
= 17,273,088,000 kbit
= 17,687,642,112,000 bits
= 2,210,955,264,000 bytes
= 2,159,136,000 kilobyte
= 2,108,531 megabytes
= 2,059 gigabytes
So that's like 4 * 500gb drives plus 1 * 120gb drive to correct for the drive maker's marketing departments.
I'm using VCD/MPEG as a basis for this, they'll invariably be using a better codec, probably with far stronger compression.
I was at the Open Tech conference and also saw this PVR box. Actually there wasn't much box to it. It consisted of several large capacity hard drives (maybe about five SATAs) and a few DVB PCI cards, connected to a motherboard on a wooden base, no case.
It recorded one WEEK's worth of video from, as far as I could tell, only the BBC's Freeview channels (BBC1, BBC2, BBC3, BBC4, News24, CBeebies, CBBC). The quality seemed fine judging from an episode of Doctor Who which went out on BBC3 the previous Thursday being projected behind the presenter.
2gb an hour sounds like a bit much, to be honest. Use DivX, Xvid, etc, and you could reasonably get it down to 500mb an hour. Use commercial skipping, probably 350. Compromise on quality a bit, maybe 250. That's 6 gb per day per channel... still not small, but it shows it as doable.
"Sometimes a woman is a kind of religion, she can save your soul & set you free from all your sins" - Bad Examples
If they're going to be making an announcement in August, then why not wait until August to post the article?
Because the system was demoed at OpenTech 2005 on Saturday.
I was there and I saw it. So here's a bit more info on how it works. I records digital terrestrial televison, not analogue. I suppose it could be changed to use satelite DVB instead of terrestrial DVB - but you can't get a DVB-S card that decode Sky's encryption, so there's not much point. It records an entire mutiplex off the DVB-T card. They only appear to have one card, so they were only recording the BBC multiplex. There are 6 multiplexes in the UK, so I suppose to record "all" DVB-T transmissions, you'd need multiple cards.
As for costs, while the DVB card was quite cheap (they said around 50 quid) and the PC is faily inexpensive, the storage costs are about the same as a plasma tv - but falling all the time.
At some point, somewhere, the entire internet will be found to be illegal.
...are you going to get a proc capable of encoding 30 divx streams simultaneously?
I am NaN
Then he spent 24 hours camping outside.
He wrote it up in 'The Age of Missing Information'. (Amazon link provided for the reviews, no sales connection.)
Great book, I recommend it.
Now excuse me, I need to get back to /. before I miss something.
Never shake hands with a man you meet in a fertility clinic.
Your calculation is flawed. You assume compressing 30 channels real-time 24/7 is possible without melting the living room.
Linux is not Windows
According to http://erg.abdn.ac.uk/research/future-net/digital- video/dvb-trans.html each DVB multiplex runs at 24Mb/s.
So, storing one multiplex for a month needs
(24/8)*60*60*24*31 Mbytes of storage = 8 Terra Bytes
So 8TB per multiplex per month just about doable at the state of the art, but not very likely.
I haven't checked how many muxes in use for different channels. I think it's about 3, so say 24TB all in. That's a lot of disks!
You assume they're recording analog broadcasts, which they aren't. Recording UK terrestrial digital broadcasts requires no compression. It's already compressed. They're directly recording the Freeview multiplexes.
If a job's not worth doing, it's not worth doing right.
Correction -- there were three DVB-T cards, not just one. Thus they could record up to three multiplexes simultaneously.
4 /in/photostream/ (Photo is a bit dark, but you can clearly see the three red LEDs on each of the tuner cards.)
See http://www.flickr.com/photos/90983090@N00/2814720
Cheers,
dwm