[gst-devel] v4l2 strangeness

[Marco Ballesio]

Hi,

On Fri, Oct 8, 2010 at 5:42 PM, Gary Thomas <gary at mlbassoc.com> wrote:

> I have an old USB webcam (Logitech QuickCam Chat) that I'm
> trying to use with v4l2src.  When I run it on slightly different
> versions of Linux & gst-plugins, I get very different results.
>
>
..snip..


> On x86 Linux 2.6.34, gstreamer-0.10.30, gstreamer-plugins-good-0.10.25,
> I get these:
>   0:00:00.037755702 22728  0x9eec050 DEBUG                   v4l2
> gstv4l2object.c:882:gst_v4l2_object_fill_format_list:<v4l2src0> getting src
> format enumerations
>   0:00:00.037806177 22728  0x9eec050 INFO                    v4l2
> gstv4l2object.c:919:gst_v4l2_object_fill_format_list:<v4l2src0> got 4
> format(s):
>   0:00:00.037831421 22728  0x9eec050 INFO                    v4l2
> gstv4l2object.c:925:gst_v4l2_object_fill_format_list:<v4l2src0>   YU12
> (emulated)
>   0:00:00.037853538 22728  0x9eec050 INFO                    v4l2
> gstv4l2object.c:925:gst_v4l2_object_fill_format_list:<v4l2src0>   YV12
> (emulated)
>   0:00:00.037886708 22728  0x9eec050 INFO                    v4l2
> gstv4l2object.c:925:gst_v4l2_object_fill_format_list:<v4l2src0>   BGR3
> (emulated)
>   0:00:00.037908230 22728  0x9eec050 INFO                    v4l2
> gstv4l2object.c:925:gst_v4l2_object_fill_format_list:<v4l2src0>   RGB3
> (emulated)
>

..snip..


> On ARM Linux 2.6.32, gstreamer-0.10.30, gst-plugins-good-0.10.25,
> I get this (but not useful) trace:
>   0:00:00.180328399   741    0x15050 INFO                    v4l2
> gstv4l2object.c:919:gst_v4l2_object_fill_format_list:<v4l2src0> got 2
> format(s):
>   0:00:00.180450469   741    0x15050 INFO                    v4l2
> gstv4l2object.c:925:gst_v4l2_object_fill_format_list:<v4l2src0>   GBRG
>   0:00:00.180603057   741    0x15050 INFO                    v4l2
> gstv4l2object.c:925:gst_v4l2_object_fill_format_list:<v4l2src0>   S561
>   0:00:00.180725127   741    0x15050 DEBUG                   v4l2
> gstv4l2object.c:1151:gst_v4l2_object_v4l2fourcc_to_structure: Unknown fourcc
> 0x47524247 GBRG
>   0:00:00.184051543   741    0x15050 DEBUG                v4l2src
> gstv4l2src.c:578:gst_v4l2src_get_caps:<v4l2src0> unknown format 1196573255
>   0:00:00.184387236   741    0x15050 DEBUG                   v4l2
> gstv4l2object.c:1151:gst_v4l2_object_v4l2fourcc_to_structure: Unknown fourcc
> 0x31363553 S561
>   0:00:00.184509307   741    0x15050 DEBUG                v4l2src
> gstv4l2src.c:578:gst_v4l2src_get_caps:<v4l2src0> unknown format 825636179
>   0:00:00.184661894   741    0x15050 INFO                 v4l2src
> gstv4l2src.c:584:gst_v4l2src_get_caps:<v4l2src0> probed caps: EMPTY
>
> Same camera, same (+/- kernel version) kernel modules, vastly
> different behaviour.  What gives?
>

the debug log is pretty self-explanatory: the webcam is using different
color formats wrt different architectures. Assuming the webcam sensor/phy
are the same and the bus used is the same (USB), I'd give a check on the
differences in the kernel module between the two releases (2.6.32 / 2.6.34).
It's also possible that the driver has some compilation flags which use
different paths wrt ARM or x86.

Regards
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