Re: Getting started with OMAP3 ISP

[Gary Thomas <gary@mlbassoc.com>]

On 2011-08-30 16:50, Laurent Pinchart wrote:
> 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 ?

It's a BT656 encoder - 8-bit UYVY 4:2:2

>
>> 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.
>

-- 
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Gary Thomas                 |  Consulting for the
MLB Associates              |    Embedded world
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