Re: Getting started with OMAP3 ISP

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Gary,

On Wednesday 31 August 2011 00:45:39 Gary Thomas wrote:
> On 2011-08-29 04:49, Laurent Pinchart wrote:
> > On Thursday 25 August 2011 18:07:38 Gary Thomas wrote:
> >> Background:  I have working video capture drivers based on the
> >> TI PSP codebase from 2.6.32.  In particular, I managed to get
> >> a driver for the TVP5150 (analogue BT656) working with that kernel.
> >> 
> >> Now I need to update to Linux 3.0, so I'm trying to get a driver
> >> working with the rewritten ISP code.  Sadly, I'm having a hard
> >> time with this - probably just missing something basic.
> >> 
> >> I've tried to clone the TVP514x driver which says that it works
> >> with the OMAP3 ISP code.  I've updated it to use my decoder device,
> >> but I can't even seem to get into that code from user land.
> >> 
> >> Here are the problems I've had so far:
> >>     * udev doesn't create any video devices although they have been
> >>     
> >>       registered.  I see a full set in /sys/class/video4linux
> >>       
> >>          # ls /sys/class/video4linux/
> >>          v4l-subdev0  v4l-subdev3  v4l-subdev6  video1       video4
> >>          v4l-subdev1  v4l-subdev4  v4l-subdev7  video2       video5
> >>          v4l-subdev2  v4l-subdev5  video0       video3       video6
> > 
> > It looks like a udev issue. I don't think that's related to the kernel
> > drivers.
> > 
> >>       Indeed, if I create /dev/videoX by hand, I can get somewhere, but
> >>       I don't really understand how this is supposed to work.  e.g.
> >>       
> >>         # v4l2-dbg --info /dev/video3
> >>         
> >>         Driver info:
> >>             Driver name   : ispvideo
> >>             Card type     : OMAP3 ISP CCP2 input
> >>             Bus info      : media
> >>             Driver version: 1
> >>             Capabilities  : 0x04000002
> >>             
> >>                     Video Output
> >>                     Streaming
> >>     
> >>     * If I try to grab video, the ISP layer gets a ton of warnings, but
> >>     
> >>       I never see it call down into my driver, e.g. to check the current
> >>       format, etc.  I have some of my own code from before which fails
> >>       miserably (not a big surprise given the hack level of those
> >>       programs).
> >>       
> >>       I tried something off-the-shelf which also fails pretty bad:
> >>         # ffmpeg -t 10 -f video4linux2 -s 720x480 -r 30 -i /dev/video2
> >> 
> >> junk.mp4
> >> 
> >> I've read through Documentation/video4linux/omap3isp.txt without
> >> learning much about what might be wrong.
> >> 
> >> Can someone give me some ideas/guidance, please?
> > 
> > In a nutshell, you will first have to configure the OMAP3 ISP pipeline,
> > and then capture video.
> > 
> > Configuring the pipeline is done through the media controller API and the
> > V4L2 subdev pad-level API. To experiment with those you can use the
> > media-ctl command line application available at
> > http://git.ideasonboard.org/?p=media- ctl.git;a=summary. You can run it
> > with --print-dot and pipe the result to dot -Tps to get a postscript
> > graphical view of your device.
> > 
> > Here's a sample pipeline configuration to capture scaled-down YUV data
> > from a sensor:
> > 
> > ./media-ctl -r -l '"mt9t001 3-005d":0->"OMAP3 ISP CCDC":0[1], "OMAP3 ISP
> > CCDC":2->"OMAP3 ISP preview":0[1], "OMAP3 ISP preview":1->"OMAP3 ISP
> > resizer":0[1], "OMAP3 ISP resizer":1->"OMAP3 ISP resizer output":0[1]'
> > ./media-ctl -f '"mt9t001 3-005d":0[SGRBG10 1024x768], "OMAP3 ISP
> > CCDC":2[SGRBG10 1024x767], "OMAP3 ISP preview":1[YUYV 1006x759], "OMAP3
> > ISP resizer":1[YUYV 800x600]'
> > 
> > After configuring your pipeline you will be able to capture video using
> > the V4L2 API on the device node at the output of the pipeline.
> 
> Getting somewhere now, thanks.  When I use this full pipeline, I can get
> all the way into my driver where it's trying to start the data.
> 
> What if I want to use less of the pipeline?  For example, I'd normally be
> happy with just the CCDC output.  How would I do that?

Then connect CCDC's pad 1 to the CCDC output video node and capture on that 
video node.

> What pixel format would I use with ffmpeg?

What does your subdev deliver ?

> n.b. I know most of these are pretty n00b questions - I'd look up the
> answers for myself, but I've had precious little success finding any
> documentation, especially on media-ctl and/or the OMAP3 ISP setups.

-- 
Regards,

Laurent Pinchart