#10204 NORM 1.0-sof: framerate limit support in cafe_ccic for XO-1

Zarro Boogs per Child bugtracker at laptop.org
Wed Jul 7 15:01:59 EDT 2010

#10204: framerate limit support in cafe_ccic for XO-1
 Reporter:  dsd     |                 Owner:  dsd                
     Type:  defect  |                Status:  new                
 Priority:  normal  |             Milestone:  1.0-software-update
Component:  kernel  |               Version:  not specified      
 Keywords:          |           Next_action:  never set          
 Verified:  0       |   Deployment_affected:                     
Blockedby:          |              Blocking:                     
 For XO-1.5 builds, Jon Corbet added support to via_camera to allow
 gstreamer to limit framerates.

 The same small changes need to be made to cafe_ccic. (I've done this
 locally, just waiting until the imminent XO-1.5 software release has been
 made before pushing)

 We should also pull Jon's latest work on the ov7670 max_frame_rate
 parameter front, allowing the value to be set in the .config. This is in
 git://git.lwn.net/linux-2.6 olpc-2.6.31-cam

 Then we need to modify the config files which involves choosing a good
 max_frame_rate value for XO-1. Jon, in #10137 you wrote "It turns out that
 the ov7670 on the XO 1.5 is clocked at 90fps." Can you explain how you
 measured this? We need to do the same for XO-1.

 Through some experimentation I've found that max_frame_rate=45 brings good
 results. This makes sense if we're using 90 for XO-1.5, as the difference
 between the laptops is that the MCLK speed was doubled(XO-1 24MHz, XO-1.5
 48MHz). It results in 30FPS when no limit is applied, and pretty good
 matching to the desired framerate limit when applied (you get 12fps when
 you ask for 10, you get 6fps when you ask for 5, 15 and 30 are pretty spot
 on). test case is http://dev.laptop.org/~dsd/20100428/fpslog.txt

Ticket URL: <http://dev.laptop.org/ticket/10204>
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