Among the many reasons netbooks have taken off, the potential to use them as portable video playback devices has to be close to the top. Their tiny dimensions coupled with relatively large screens and essentially universal file format support makes them ideal for watching a couple of movies on a long flight or catching up with the latest episode of Top Gear while on the bus. It's therefore essential that the CPUs in these machines are able to cope with playing back video to a satisfactory level - something that the VIA C7 powered, HP 2133 Mini-note proved was far from a given.
It's also important to consider the power usage of the platforms when playing back video as it's a relatively taxing process so could potentially drain batteries very quickly.
Now testing video isn't necessarily that easy as all the different formats/codecs/bit rates available mean there is a near infinitie combination of processing requirements. This in turn means power consumption figures can vary massively dependingt on what sort of video you're watching. Something like YouTube uses a very low bit rate and a basic codec that doesn't require much processing so will certainly run on these CPUs and should draw very little power in the process. Likewise decoding low resolution (320 x 240) DivX video is a relatively easy task but when this resolution is blown up to fill the 9in or 10in screen of your netbook it will look pretty awful.
The ideal, then is that these CPUs can cope with playing at least 480p (704 x 480) resolution video recorded in either MPEG4 part 2 (i.e. DivX, Xvid, Quicktime 6) or MPEG4 part 10 (h.264, Quicktime 7, Blu-ray), and preferably even cope with 720p (1280 x 720). And, that they can do this without drawing ludicrous amounts of power.
So, to test we downloaded the 480p and 720p versions of the trailer for Will Smith's latest film, Hancock. These are recorded using the h.264 codec so they are very good quality for their size and make for very satisfactory watching. Unfortunately h.264 is very CPU intensive so it can potentially draw a large amount of power.
Next we played the same Doctor Who clip we use in our video encoding test, both in its original 576i MPEG2 format and its compressed 512 x 410 Xvid format.
Both systems brushed aside the Doctor Who clips without so much as breaking a sweat and they seemed to cope well with the 480p as well. Indeed CPU utilisation while playing the 480p footage remained well below 50 per cent, which would suggest you may even be able to do a bit of multi-tasking without having too many problems with the video stuttering. Unfortunately we tested this and while Nano could just about cope, Atom simply couldn't.
It wasn't quite such a rosy picture for 720p playback. Neither system came close to being able to playback our video clip. This is hardly a surprise but it's nonetheless interesting to see, especially as VIA was claiming that Nano could even cope with 1080p video. Presumably it was using a less CPU intensive codec than h.264 to demonstrate this.
Either way, though, the ability to playback 480p video recorded in h.264 makes for a very pleasant viewing experience so either CPU should serve you fine.