[libcamera-devel] [PATCH v5 1/6] libcamera: stream: add initial Stream class

[Laurent Pinchart]

Hi Niklas,

Thank you for the patch.

On Wed, Jan 30, 2019 at 12:56:10PM +0100, Niklas Söderlund wrote:
> Add an initial Stream implementation. The idea is that once capability
> support is added to the library each stream will describe its
> capabilities using this class. An application will then select one or
> more streams based on these capabilities and use them to configure the
> camera and capture.
> 
> At this stage the Stream class is empty as capabilities are yet to be
> added. The class is still useful as it will be used to communicate how
> many streams a Camera object provides.
> 
> Signed-off-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
> Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> ---
>  include/libcamera/libcamera.h |  1 +
>  include/libcamera/meson.build |  1 +
>  include/libcamera/stream.h    | 18 +++++++++++++
>  src/libcamera/meson.build     |  1 +
>  src/libcamera/stream.cpp      | 51 +++++++++++++++++++++++++++++++++++
>  5 files changed, 72 insertions(+)
>  create mode 100644 include/libcamera/stream.h
>  create mode 100644 src/libcamera/stream.cpp
> 
> diff --git a/include/libcamera/libcamera.h b/include/libcamera/libcamera.h
> index 6619e556ebbd20e4..8167e8099ac061d2 100644
> --- a/include/libcamera/libcamera.h
> +++ b/include/libcamera/libcamera.h
> @@ -13,6 +13,7 @@
>  #include <libcamera/event_dispatcher.h>
>  #include <libcamera/event_notifier.h>
>  #include <libcamera/signal.h>
> +#include <libcamera/stream.h>
>  #include <libcamera/timer.h>
>  
>  #endif /* __LIBCAMERA_LIBCAMERA_H__ */
> diff --git a/include/libcamera/meson.build b/include/libcamera/meson.build
> index 8fcbbf7892ea9280..8c14423bc444ef51 100644
> --- a/include/libcamera/meson.build
> +++ b/include/libcamera/meson.build
> @@ -6,6 +6,7 @@ libcamera_api = files([
>      'event_notifier.h',
>      'libcamera.h',
>      'signal.h',
> +    'stream.h',
>      'timer.h',
>  ])
>  
> diff --git a/include/libcamera/stream.h b/include/libcamera/stream.h
> new file mode 100644
> index 0000000000000000..4f47d85ed6382b36
> --- /dev/null
> +++ b/include/libcamera/stream.h
> @@ -0,0 +1,18 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2019, Google Inc.
> + *
> + * stream.h - Video stream for a Camera
> + */
> +#ifndef __LIBCAMERA_STREAM_H__
> +#define __LIBCAMERA_STREAM_H__
> +
> +namespace libcamera {
> +
> +class Stream final
> +{
> +};
> +
> +} /* namespace libcamera */
> +
> +#endif /* __LIBCAMERA_STREAM_H__ */
> diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
> index b5b25965fd123350..a4e9cc8f936c47a7 100644
> --- a/src/libcamera/meson.build
> +++ b/src/libcamera/meson.build
> @@ -11,6 +11,7 @@ libcamera_sources = files([
>      'media_object.cpp',
>      'pipeline_handler.cpp',
>      'signal.cpp',
> +    'stream.cpp',
>      'timer.cpp',
>      'v4l2_device.cpp',
>  ])
> diff --git a/src/libcamera/stream.cpp b/src/libcamera/stream.cpp
> new file mode 100644
> index 0000000000000000..f82b05a2bcfa14e9
> --- /dev/null
> +++ b/src/libcamera/stream.cpp
> @@ -0,0 +1,51 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2019, Google Inc.
> + *
> + * stream.cpp - Video stream for a Camera
> + */
> +
> +#include <libcamera/stream.h>
> +
> +/**
> + * \file stream.h
> + * \brief Video stream for a Camera
> + *
> + * A camera device can provide frames in different resolutions and formats
> + * concurrently from a single image source. The Stream class represents
> + * one of the multiple concurrent streams.
> + *
> + * All streams exposed by a camera device share the same image source and are
> + * thus not fully independent. Parameters related to the image source, such as
> + * the exposure time or flash control, are common to all streams. Other
> + * parameters, such as format or resolution, may be specified per-stream,
> + * depending on the capabilities of the camera device.
> + *
> + * Camera devices expose at least one stream, and may expose additional streams
> + * based on the device capabilities. This can be used, for instance, to
> + * implement concurrent viewfinder and video capture, or concurrent viewfinder,
> + * video capture and still image capture.
> + */
> +
> +namespace libcamera {
> +
> +/**
> + * \class Stream
> + * \brief Video stream for a camera
> + *
> + * The Stream class models of all static information which are associated

s/models of/models/

> + * with a single video stream. Streams are exposed by the Camera object they
> + * belong to.
> + *
> + * Cameras are capable of supplying more then one stream from the same video

s/Cameras are capable of supplying/Cameras may supply/

(as not all cameras are capable of supplying multiple streams)

s/then/than/

Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

> + * source. In such cases an application can inspect all available streams and
> + * select the ones that best fit its use case.
> + *
> + * \todo Add capabilities to the stream API. Without this the Stream class only
> + * serves to reveal how many streams of unknown capabilities a camera supports.
> + * This in itself is productive as it allows applications to configure and
> + * capture from one or more streams even if they won't be able to select the
> + * optimal stream for the task.
> + */
> +
> +} /* namespace libcamera */

-- 
Regards,

Laurent Pinchart