Maxtor champions 6 stream DVRs
132Mbps? Bring it on
Maxtor and Scientific Atlanta last week attracted column inches on their plans for the next generation of DVRs, due for release in about 18 months. But what exactly are they talking about when they boast of 6 stream technology?
To date, pegging the price of DVRs and VCRs meant that they could feature a limited number of tuners. A tuner sorts through the signals on a TV network - digital or analogue - and selects the wavelength carrying the required programme. The tuner then unscrambles it and readies it for viewing pleasure. In the past, including two tuners was thought to be an extravagance, and any more than that completely unnecessary.
The rationale behind this was that the single-TV consumer would be unlikely to want to record more than two programs at a time, while either watching one of them or watching a third recorded program.
With the advent of home networks, and with three or more TVs in the house, many households will, in future, want to watch multiple recorded streams. What's more, there may still be the requirement to be recording up to two further channels - at least. This means that 6 concurrent video streams need to be supported.
And this is why a disk manufacturer - Maxtor - has weighed into the debate: to address the thorny problem of getting enough data off a hard disk to support multiple concurrent video streams.
Existing TV formats require a stream of about 270 megabits per second or 34 megabytes per second, in raw video. MPEG or other compression crushes this down dramatically to around 675 kilobits per second or even less with the new H.264 codecs. Six such streams would require a disk-reading speed of only 4 megabits per second.
But if we consider HDTV, then suddenly the streams could be far larger: possibly 22 megabits a second for each stream after compression. Furthermore, roughly four times the speed would be required, because there are so many more bits to convey due to the 1080 by 1280 maximum pixel numbers per frame.
Six of these would add up to 132 megabits per second - child’s play to a disk drive, as long as doesn’t have to spend all of its time moving from one stream to another and ragging its heels with seek times and latency. Latency, btw, is the time spent looking up where the data is and waiting for the part of the disk it needs to come round to the actuator.
Maxtor this week completed tests on a device which had two separate ports. It's unclear if these were two actuators, but it sounds like it. These combined to yield I/O transfers of 3 gigabits per second. A hard drive delivering multiple video streams would need multiple reading heads (actuators) to optimize delivery and lower seek times and latency.
It's clear that since average US household has close to 4 TVs and consumers are increasingly embracing HDTV, Wi-Fi networks and now have the possibility of ultra-wide band within a year for home networking, future DVR players are likely to need to manage that many video streams to stay at the heart of home entertainment.
The machine of the future will indeed need to be all-singing, all dancing. Sony’s PSX design demonstrates that once DVRs are established, many more features will be required to stay ahead of the game - a DVD writer, a high density Blu Ray DVD writer, an inbuilt games console, a hi-fi music player, the list goes on.
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