I hope you meant 40 megabits per second(Mbps) and not megabytes(MBps).

1280 pixels * 720 pixels * 30 frames per second * 12 bits per pixel (this would be 24 if the camera sends data in RGB and not YUV, that is, double) = 331776000 bits per second
Divide by 8: 41472000 bytes/second
divide by 1024*1024: 39.55... megabytes/second
Double that if it's RGB..

That would be correct for a raw sensor dump - it never leaves the camera, as it actively works differently in video and camera mode. It delivers a partially compressed stream in whatever mode that is, otherwise there would be no HD cameras, at 250M/s the data is too much for any portable storage system (even a SSD).

Also, there is no way that tiny unshielded connector phone cameras or video cameras have can take 250M/s. that would mean at least a 2Gb link.

Not even DSLRs deliver uncompressed raw data, all real life RAW formats I know are compressed. My A200, e.g., delivers 10M at 12 b/plane (48 bit, 6 byte), that's at least 60 MB of data, in a RAW 5-10 MB in size.

It's not entirely impossible to do it like that but I don't know of a single device (other than dedicated capture systems) that delivers raw data like that. Actually, I do, but it's way, way beyond the scope of this discussion.

Compression does not mean loss of data. So there is no need to pump out uncompressed raw data to storage directly. It's all compressed and decompressed on the fly usually by a dedicated image processor of some sort.

We already know that N900's hardware is capable of much more than what Nokia made it do. Obviously they didn't want the N900 to be their HD capable phones. That's reserved for the upcoming N8 and later models.

No, not necessarily. Though I don't expect any lossless compression from such a compact and low powered device. Also, it's entirely possible this wasn't a Nokia decision, it could be a restriction by manufacturer.

htc desire got an update of android yday. and now can record 720p. surely this is possible with n900. is this being developed? or is it not possible? the hd recording on the desire looks really good

Can only hope Nokia give a toss but release 1.2 is most likely the last well hear from Nokia.

I still find it very odd that my N9 could record video stutter-free, but my N900 with better HW cannot. I didnt expect the quality to be superb, but to record a video without lag shouldt really be an issue.. It makes me sad.

IMHO the video recording is stuttering even now with stock speeds (haven't really stress tested with PR1.2), so unless there is underutilized hardware, or worse, not utilized at all, and an update from Nokia, there is not much to do. The hardware can do only so much...

True. But the N900 hardware should at least give us stutter-free recording with the stock res.