Bug 454534 - gstreamer's v4l2src incompatible with some progressive video cameras
Summary: gstreamer's v4l2src incompatible with some progressive video cameras
Alias: None
Product: Fedora
Classification: Fedora
Component: gstreamer-plugins-good
Version: 9
Hardware: All
OS: Linux
Target Milestone: ---
Assignee: Adam Jackson
QA Contact: Fedora Extras Quality Assurance
Depends On:
Blocks: FedoraOLPCDelta
TreeView+ depends on / blocked
Reported: 2008-07-08 21:40 UTC by Daniel Drake
Modified: 2008-11-26 17:10 UTC (History)
1 user (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Last Closed: 2008-11-26 17:10:55 UTC

Attachments (Terms of Use)
patch (2.80 KB, patch)
2008-07-08 21:40 UTC, Daniel Drake
no flags Details | Diff

System ID Priority Status Summary Last Updated
GNOME Bugzilla 541956 None None None Never

Description Daniel Drake 2008-07-08 21:40:30 UTC
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

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

I questioned this driver inconsistency here:
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

Please include my patch which has been accepted upstream:

Comment 1 Daniel Drake 2008-07-08 21:40:30 UTC
Created attachment 311318 [details]

Comment 2 Fedora Update System 2008-07-21 15:14:48 UTC
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 07:12:58 UTC
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 13:09:54 UTC
Daniel can you confirm if this issue is now fixed?

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