In part one of this series, we discovered why anything recorded onto the hard disk of DVD recorders with hard drive capability has to be in DVD quality. Here in part two we will see why this fact effectively prevents the viable manufacture of models with twin digital tuners.
The fact is that the process of converting digital broadcasts to DVD quality is very hard work, and there is a dedicated processor in the machine to carry it out. With twin tuners, assuming that any programme received could be recorded and then selected for burning to DVD, you would need two of these dedicated processors, which would put the price of the machine up a lot as the specification of the whole machine would need to be much higher.
But why not have one digital tuner just for watching live programmes in whatever quality they happen to be in, and a second digital tuner connected to the hard drive just for recording, which would have all its signals converted to DVD quality in the usual way?
This would seem sensible, because you would only need one dedicated processor to convert the signal from the one tuner into DVD quality; namely the one connected to the hard drive and DVD recorder. The tuner being viewed "live" could be viewed as it stands, as the signal would never be recorded to DVD and so would not need to be converted to DVD quality.
On the face of it, this sounds workable, but in practice it would be complicated for the average consumer. You would have no "pause live TV" function, because that requires hard disk use and everything on the hard disk has to be converted to DVD quality. You would also be able to record only from the one tuner and not from the other, so this would make the recording interface more complicated. It would appear as if the second tuner were completely separate from everything else in the box. It would look to the consumer as if it had been bolted on at the last minute rather than being an integral part of the machine.
So, as you can see, having twin tuners in DVD recorders with hard drive functionality is a complicated business and not something that can currently be achieved very satisfactorily without adding significantly to the cost of the machine.
Given that the average new LCD TV has a built-in digital tuner, DVD manufacturers probably reason that this is a good enough solution to the problem of how to watch one digital channel and record another. It avoids them having to build new and much more expensive DVD recorders with hard drive functionality to overcome the above complex technical issues.
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