On Sun, 19 Dec 2010, Andy Walls wrote: > Theodore, > > Aside from detect measurment of the power line, isn't a camera the best sort of sensor for this measurment anyway? > > Just compute the average image luminosity over several frames and look for (10 Hz ?) periodic variation (beats), indicating a mismatch. > > Sure you could just ask the user, but where's the challenge in that. ;) > > Regards, > Andy Well, if it is "established policy" to go with doing this as a control, I guess we can just go ahead instead of doing something fancy. But it is nice to hear from you. Here is why. The camera in question is another jeilinj camera. Its OEM software for that other OS does present the option to choose line frequency. It also asks for the user to specify an image quality index. I can not recall that the software I got with my camera did any such thing. As I recall, it merely let the camera to start streaming. Bur at the moment I have no idea where I put that old CD. So, while I have you on the line, do you recall whether or not the OEM software for the camera you bought for your daughter present any such setup options? The new camera may be different in some particulars from the ones we have. It does have a new Product number, so apparently Jeilin might not have thought it is identical to the other ones. It does use a slightly different initialization sequence. Therefore, the quick-and-dirty way to support it would be just to introduce a patch which has switch statements or conditionals all over the place, and just to support whatever the camera was observed to do. However, that is obviously dirty as well as quick. While playing around with the code a bit, I have managed to make my old camera work with essentially the same init sequence that the new one is using. If this can be done right, it would clear a lot of crud out of the driver code. Unfortunately, doing it right involves testing... Finally, one concern that I have in the back of my mind is the question of control settings for a camera which streams in bulk mode and requires the setup of a workqueue. The owner of the camera says that he has "encountered no problems" with running the two controls mentioned above. Clearly, that is not a complete answer which overcomes all possible objections. Rather, things are OK if and only if we can ensure that these controls can be run only while the workqueue that does the streaming is inactive. Somehow, I suspect that the fact that a sensible user would only run such commands at camera setup is an insufficient guarantee that no problems will ever be encountered. So, as I said, the question of interaction of a control and a workqueue is another problem interesting little problem. Your thoughts on this interesting little problem would be appreciated. As I said, Merry Christmas :-) Theodore Kilgore -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
