[libcamera-devel] [PATCH 0/3] Sequence Observer

[Laurent Pinchart]

Hi Kieran,

On Fri, Apr 29, 2022 at 09:34:31PM +0200, Kieran Bingham via libcamera-devel wrote:
> This fell out of some more work I did in the past catching and detecting
> frame drops in streams. While the method of reporting this event to
> userspace is debated, this pulls out some core functionality and wraps
> some generic code into a Sequence Observer to provide an easy to use
> check on any monotonic sequence.
> 
> For now - it simply reports a warning if a V4L2 device detects a frame
> drop, which is more notification that we have currently... as we are
> silently dropping frames at the moment.

Even if we haven't finalized the way to handle frame drops in the
application-facing API, I think it's useful to be able to be notified of
frame drops already. I'm however thinking that the sequence observer
class is a bit overkill at this point. I'd recommend starting with an
ad-hoc solution in V4L2VideoDevice only, and later extend it if
required.

> Kieran Bingham (3):
>   libcamera: Add sequence value observer
>   test: Add Sequence observer tests
>   libcamera: v4l2: Detect frame drops on V4L2VideoDevice
> 
>  include/libcamera/internal/v4l2_videodevice.h |  2 +
>  include/libcamera/meson.build                 |  1 +
>  include/libcamera/sequence.h                  | 20 +++++
>  src/libcamera/meson.build                     |  1 +
>  src/libcamera/sequence.cpp                    | 66 +++++++++++++++
>  src/libcamera/v4l2_videodevice.cpp            | 10 +++
>  test/meson.build                              |  1 +
>  test/sequence.cpp                             | 80 +++++++++++++++++++
>  8 files changed, 181 insertions(+)
>  create mode 100644 include/libcamera/sequence.h
>  create mode 100644 src/libcamera/sequence.cpp
>  create mode 100644 test/sequence.cpp

-- 
Regards,

Laurent Pinchart