How to handle pixel format synonyms ("YUYV" is also known as "YUY2")?

[Nicolas Dufresne]

Le vendredi 31 août 2018 à 03:00 +0000, Matthew Thyer a écrit :
> Thanks Nicolas,
> 
> In experimenting with the command line "gst-device-monitor-1.0", I'm
> wondering how to get it to report on the FLIR (previously Point Grey
> Research) Blackfly S BFS-U3-13Y3C industrial camera that I need to
> work with.
> This is not a V4L2 device and the GStreamer source element I use for
> it is "aravissrc" from the "aravis" plugin that I've built for git
> master from Project Aravis (https://github.com/AravisProject/aravis).
> This camera is a "genicam" camera and would typically be addressed by
> name:
> aravissrc name=PointGrey-0115138B ! capsfilter...
> However, if it's

The aravis plugin should implement a GstDeviceProvider and register it.
Then it will work automatically (including in app like Cheese). The
provider is a feature one can provide in a GStreamer plugin, just like
GstElement or GstTypeFinder, etc.

> 
> I've tried the following:
> $ gst-device-monitor-1.0 --gst-plugin-path=/usr/local/aravis-
> 0.5/lib/gstreamer-1.0 --gst-plugin-load=aravis Video/Source:video/x-
> raw --follow
> 
> And then plugging in the USB 3 camera device but nothing appears...
> For that matter, I cannot even get the "Logitech HD Webcam C270" V4L2
> camera to be reported on via this hot plugging method.
> (The Logitech camera will be reported on if it's connected when I run
> gst-device-monitor-1.0).

By setting the plugin path, you probably lost the V4L2 plugin, at least
this is my guess. Try and setup a both path, with a : in between.

> 
> Do I need to do something with udev for this?
> 
> I currently have a file "/etc/udev/rules.d/aravis.rules" with
> content:
> # Point Grey Research
> SUBSYSTEM=="usb", ATTRS{idVendor}=="1e10", MODE:="0666",
> TAG+="uaccess", TAG+="udev-acl"

No, this rule is strictly to give normal user read/write access (on
local login I believe).

> 
> Thanks in advance
> 
> -----Original Message-----
> From: gstreamer-devel <gstreamer-devel-bounces at lists.freedesktop.org>
> On Behalf Of Nicolas Dufresne
> Sent: Wednesday, 29 August 2018 9:18 PM
> To: Discussion of the development of and with GStreamer <
> gstreamer-devel at lists.freedesktop.org>
> Subject: Re: How to handle pixel format synonyms ("YUYV" is also
> known as "YUY2")?
> 
> Le mercredi 29 août 2018 à 02:28 +0000, Matthew Thyer a écrit :
> > I'm working on an application to serve hardware accelerated
> > H.264/AVC
> > video via RTSP. I'm using the GStreamer RTSP Server 1.14.2 (built
> > from
> > source) and (currently) a Video 4 Linux 2 source.
> 
> [snip...]
> 
> > This would be fine excepting for the problem of pixel format
> > synonyms
> > (i.e. in particular, "YUYV" is also known as "YUY2").
> 
> There is no standard for fourcc, as a side effect, the GStreamer
> chosen one does not match the V4L2 one. Though, this does not matter,
> the translation is handled by GStreamer. Instead of calling into V4L2
> API to enumerate the formats, you should use the GstDeviceMonitor API
> to track and enumerate cameras. This way, you're application becomes
> V4L2 agnostic, and a transition to pipewire could be made possible.
> 
> [snip...]
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