#56 bug in v4l2 driver prevents non integer exposure times

[Craig Warner]

I'm developing an INDI client to run a DMK CCD from The Imaging Source (a video 4 linux compatible camera) and noticed a bug in the v4l2driver that I am unable to take non-integer exposure times. For instance, I set the element CCD_EXPOSURE_VALUE (in property CCD_EXPOSURE) to 0.5 and it results in Exposure (Absolute) being set to 0 and a 0 second exposure. If I set CCD_EXPOSURE_VALUE to 1.5, it seets Exposure (Absolute) to 10000 and takes a 1 second exposure.

I looked through your source code and found out where the problem is. In drivers/video/v4ldriver.h, in your struct img_t, you define expose to be an int. Then in v4l2driver.cpp, in method V4L2_Driver::ISNewNumber, you set V4LFrame->expose = values[0]; where V4LFrame is a struct of type img_t. This implicitly casts values[0], which is a double, and the value input into CCD_EXPOSURE_VALUE, as an int, truncating the value. After this, you call rc = setManualExposure(V4LFrame->expose);. The method setManualExposure already takes a double (duration) as its argument and sets AbsExposureN->value = duration * 10000; where AbsExposureN is the Exposure (Absolute) element and the actual exposure time in 1/10000s of a second sent to the CCD.

Therefore to me it looks like this issue would be completely fixed by simply changing expose from an into to a double in the struct img_t. Thanks!

Craig Warner
University of Florida

[Craig Warner]

*from an int to a double

[Jasem Mutlaq]

v4ldriver.h is used only by legacy V4L1 drivers. indi_v4l2_ccd driver (which is used for DMK) uses v4l2driver.h which already has exposre as double. What driver are you using with your DMK?

[Craig Warner]

Hmm, you're right about that. Somehow its being cast as an int somewhere else then. I'm using the v4l2_ccd driver:
indiserver -vvv indi_lx200gps indi_v4l2_ccd

Here is some output from very very verbose mode showing the problem:
set CCD_EXPOSURE_VALUE = 1.5

2014-11-07T21:14:14: Client 0: read newNumberVector V4L2 CCD CCD_EXPOSURE
CCD_EXPOSURE_VALUE='1.5'
2014-11-07T21:14:14: Driver indi_v4l2_ccd: queuing responsible for <newnumbervector device="V4L2 CCD" name="CCD_EXPOSURE">
2014-11-07T21:14:14: Client 8: queuing <newnumbervector device="V4L2 CCD" name="CCD_EXPOSURE"></newnumbervector></newnumbervector>

Image header shows EXPTIME = 1.5
EXPTIME = 1.5 / Total Exposure Time (s)

However it sets Exposure (Absolute) to 10000:
2014-11-07T21:14:14: Driver indi_v4l2_ccd: read defNumberVector V4L2 CCD Image Adjustments Idle rw
Brightness='0'
Gamma='100'
Gain='260'
Exposure (Absolute)='10000'
2014-11-07T21:14:14: Client 0: queuing <defnumbervector device="V4L2 CCD" name="Image Adjustments">
....
2014-11-07T21:14:14: Client 8: sending msg copy 1 nq 28:
<newnumbervector device="V4L2 CCD" name="CCD_EXPOSURE">
<onenumber name="CCD_EXPOSURE_VALUE">
1.5
</onenumber>
</newnumbervector>
....
2014-11-07T21:14:14: Client 8: sending msg copy 1 nq 20:
<defnumbervector device="V4L2 CCD" name="Image Adjustments" label="" group="V4L2 Control" state="Idle" perm="rw" timeout="60" timestamp="2014-11-07T21:14:14">
<defnumber name="Brightness" label="Brightness" format="%0.f" min="0" max="63" step="1">
0
</defnumber>
<defnumber name="Gamma" label="Gamma" format="%0.f" min="1" max="500" step="1">
100
</defnumber>
<defnumber name="Gain" label="Gain" format="%0.f" min="260" max="1023" step="1">
260
</defnumber>
<defnumber name="Exposure (Absolute)" label="Exposure (Absolute)" format="%0.f" min="1" max="36000000" step="1">
10000
</defnumber>
</defnumbervector></defnumbervector>

The actual counts are the same level as when I do a 1 second exposure (and half that of when I take a 2 second exposure) so it definitely exposed for the time contained in Exposure (Absolute). I'll continue to look through the code to see if I can figure out where it is getting cast as an int. For the record, here's the version I'm using:
INDI Library: 0.9.8
Code $Revision: 726523 $. Protocol 1.7.

Thanks!