#12693 NORM Future : Solve mess with Xv image display with unaligned planes

Zarro Boogs per Child bugtracker at laptop.org
Fri May 31 15:51:36 EDT 2013

#12693: Solve mess with Xv image display with unaligned planes
 Reporter:  dsd              |                 Owner:  dsd           
     Type:  defect           |                Status:  new           
 Priority:  normal           |             Milestone:  Future Release
Component:  x window system  |               Version:  not specified 
 Keywords:                   |           Next_action:  never set     
 Verified:  0                |   Deployment_affected:                
Blockedby:                   |              Blocking:                
 http://bugs.sugarlabs.org/ticket/4491 has a test case that fails on 13.2.0
 on XO-4.

 Playing back a 400x300 theora file causes Xv to be passed an I420 image
 where the U/V planes are not 64-byte aligned.

 In xf86-video-dove DovefbPutImageTextured we call gco2D_FilterBlit() but
 through experimentation I have determined that that call only succeeds
 when the Y, U and V planes are 64-byte aligned.

 In theory, we can modify QueryImageAttributes to tell Xv clients where to
 put each plane in memory, making them meet this limitation. In practice,
 gstreamer doesn't honor that

 Another option may be to enable one of the other Xv codepaths in xf86
 -video-dove, such as the mixed one, which can perhaps be persuaded to use
 FilterBlit for well-aligned images, and the slower fallback method for

 It would also be interesting to know why this same test case works on
 XO-1.75 on 13.2.0. Is it due to a small difference in the DDX, a
 difference in the galcore versions between the two platforms, or a
 limitation that appears to come from hardware?

 For now Record has been modified to create well-aligned image data, but we
 will face problems playing back videos at some non-standard resolutions
 (well, we already do, in other tickets...).

Ticket URL: <http://dev.laptop.org/ticket/12693>
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