- OMX_CONFIG_CAMERASETTINGSTYPE and MMAL_PARAMETER_CAMERA_SETTINGS_T.
They are the same thing, but in both cases they are read only. If you want to set particular values, then there are already parameters exposing almost all those settings (ISO sets up both analog and digital gain).
NB nLux that is in OMX_CONFIG_CAMERASETTINGSTYPE is no longer supported, hence missing it out of the MMAL parameter.
As has been put on other forum posts, setting the shutter speed on the sensor is done as a number of extra lines to read out as temporal padding. The register to set this is 16bit IIRC. The line length of the different sensor modes varies, and on the binned mode it maxes out at 772ms. For the full 5MPix mode it maxes out at something like 1.07s. The cropped 1080P mode was about 997ms.
If the AGC tuner is allowed free-reign, then on capture it will extend shutter speed beyond the value that preview was running in and decrease gain to get back to the same overall scene exposure. If a fixed shutter speed has been set, then the value has already been clipped and isn't rerequested.
We are trying to get the binned mode (and others) to support longer exposure times, but either you then have to compromise the max framerate, or end up having to reprogram PLLs and other things on the fly - not a task to be undertaken lightly. It's all down to time though, and that is in short supply at the moment.
- ISO 800+
I haven't got the tuner settings to hand, but each mode has a max combined gain that is allowed. Analog gain is limited by the sensor to x8 (ie ISO 800), and we don't recall any mode ever allowing the combined value to be above x16 due to excessive noise. Night mode normally allows everything to be cranked up as high as they can go, so it is normally the best bet as an automatic mode. I can't remember the detail of manually setting ISO modes and what that will allow.
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