Forum > Sony Ericsson / Sony > Software, Firmware and Drivers > c905 VGA recording hack?

I want give us a little explication:

I dont want to "criticize", but yours VGA mods are very poor. You can record video to VGA resolution, yes, but in the best case you only obtain 7-12fps, depending scene complexity. You can force to 15fps if you want, and 24 or 30, only need change a pair of numbers, but this change dont mean you obtain this framerate.

For example, the video upload by eltoffer with her 3.61 version. You can analyze the video and you can view that the máximun fps are 11 (it dont bit). Anyone dont trust me, i can post some images.

And this its very simple. The clock of this camera its setting to 13MHz (Master Clock its double, but its used for other things). But a 640*480 resolution for 15fps (for example) need a little more power. A simple example:

C905 camera capture video in YUV422/YUV420. YUV422/YUV420 need read 4bytes per output pixel (if i remember)

CLK 13MHZ similar to said that can read 13.000.000 bytes per second.

QVGA= 320*240 -> 320*240*4 = 307200 -> 13*10^6 / 307200 = 42.3fps max
VGA = 640*480 -> 640*480*4 = bla bla bla = 10.57fps max

Of course this its relative, you can obtain in some times a little more/less.

If you want a pure VGA at 15fps you need:

640*480*4*15 = 18432000 Hz = 18.5MHz aprox, 19MHz

this mean you must overclock the stock 13MHz clk to at least 19MHz. This can be done in camera driver. The problems? Its can be... dangerous. Always its possible a little margin in OC, but nobody know never the max threshold. My be 19MHz can be safe, maybe no

VGA at 15fps = 19MHz -> Must be safe and stable
VGA at 20fps = 24.5 -> 25MHz -> Can be safe and stable
VGA at 25fps = 30.7 -> 31MHz -> The most probable its very dangerous for cam integrity


In other point, this its only the first problems. Exist other: bitrate. If you want obtain a good quality you need a good bitrate (depending of course of codec). C905 take videos in MPGE-4 part 2 (Im sure that SP profile only) and h263 for videoconference only. In both cases, at a target bitrate of 768. With MPEG4 part 2 SP, 768 can be sufficient for 320*480 30fps, but for 640*480 at 15fps you obtain clearly much less quality. For 640*480 at 20 you obtain less. If you want obtain a similar quality at 640*480 at 20fps you need at least about >1.5Mbps.

Looking into camdriver maybe its possible make a mod to take video in pure YUV, so you can obtain a max quality for video recording with a "expensive" memory size

cheers.