Bug 454534 - gstreamer's v4l2src incompatible with some progressive video cameras
gstreamer's v4l2src incompatible with some progressive video cameras
Status: CLOSED CURRENTRELEASE
Product: Fedora
Classification: Fedora
Component: gstreamer-plugins-good (Show other bugs)
9
All Linux
low Severity low
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Assigned To: Adam Jackson
Fedora Extras Quality Assurance
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Depends On:
Blocks: FedoraOLPCDelta
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Reported: 2008-07-08 17:40 EDT by Daniel Drake
Modified: 2008-11-26 12:10 EST (History)
1 user (show)

See Also:
Fixed In Version:
Doc Type: Bug Fix
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Last Closed: 2008-11-26 12:10:55 EST
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RHEL 7.3 requirements from Atomic Host:
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Attachments (Terms of Use)
patch (2.80 KB, patch)
2008-07-08 17:40 EDT, Daniel Drake
no flags Details | Diff


External Trackers
Tracker ID Priority Status Summary Last Updated
GNOME Desktop 541956 None None None Never

  None (edit)
Description Daniel Drake 2008-07-08 17:40:30 EDT
Description of problem:
v4l2src only uses V4L2_FIELD_INTERLACED which is a whole-frame capture mode (it
requests interlaced video where the two fields have already been merged
together).

However most webcams only offer progressive video (i.e. V4L2_FIELD_NONE) and
will reject any requests for interlaced video. Other drivers will only offer
progressive and will silently 'correct' gstreamer's request for interlaced
video.

I questioned this driver inconsistency here:
http://marc.info/?l=linux-video&m=121434022130546&w=2
And Mauro then told me on IRC that both behaviours are correct: it's fine for
drivers to reject unsupported fields with -EINVAL, and it's also fine for
simple drivers to silently fix up the user's request.

So in order to speak to a wider number of cameras, gstreamer should tolerate
the fact that drivers may reject a request for interlaced images with -EINVAL
and should then retry for progressive (Mauro confirmed this approach is the
best we have at the moment).

This patch also allows OLPC to drop a patch that we needed to get the XO webcam
working: http://dev.laptop.org/attachment/ticket/7294/v4l2-nointerlace.patch
http://dev.laptop.org/ticket/7294




Please include my patch which has been accepted upstream:
http://bugzilla.gnome.org/show_bug.cgi?id=541956
Comment 1 Daniel Drake 2008-07-08 17:40:30 EDT
Created attachment 311318 [details]
patch
Comment 2 Fedora Update System 2008-07-21 11:14:48 EDT
gstreamer-plugins-good-0.10.8-8.fc9 has been submitted as an update for Fedora 9
Comment 3 Fedora Update System 2008-07-23 03:12:58 EDT
gstreamer-plugins-good-0.10.8-8.fc9 has been pushed to the Fedora 9 testing repository.  If problems still persist, please make note of it in this bug report.
 If you want to test the update, you can install it with 
 su -c 'yum --enablerepo=updates-testing update gstreamer-plugins-good'.  You can provide feedback for this update here: http://admin.fedoraproject.org/updates/F9/FEDORA-2008-6621
Comment 4 Peter Robinson 2008-10-25 09:09:54 EDT
Daniel can you confirm if this issue is now fixed?

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