[libcamera-devel] [PATCH v2 7/8] libcamera: camera: Add CameraConfiguration
Niklas Söderlund
niklas.soderlund at ragnatech.se
Fri Apr 5 14:01:59 CEST 2019
Hi Jacopo,
Thanks for your feedback.
On 2019-04-05 13:12:11 +0200, Jacopo Mondi wrote:
> Hi Niklas,
>
> On Fri, Apr 05, 2019 at 12:21:07PM +0200, Niklas Söderlund wrote:
> > Hi Jacopo,
> >
> > Thanks for your feedback. I will just address conceptual thing in this
> > reply and circle back to the nitty-gritty details in an other reply :-)
> >
> > On 2019-04-05 11:47:46 +0200, Jacopo Mondi wrote:
> > > Hi Niklas,
> > > thanks for the patch.
> > >
> > > On Fri, Apr 05, 2019 at 04:02:55AM +0200, Niklas Söderlund wrote:
> > > > To properly support both multiple streams and usages the library must
> > > > provide a method to map the stream usages to the returned stream
> > > > configuration. Add a camera configuration object to handle this mapping.
> > > >
> > > > Applications can iterate over the returned camera configuration to
> > > > retrieve the streams selected by the library in the same order as the
> > > > usages it provided to the library. Further more the application can use
> > >
> > > "in the same order as it provided usages to the library"
> > >
> > > furthermore
> > >
> > > > the streams to retrieve there configuration using operator[] of the
> > >
> > > "a stream pointer to retrieve its configuration" or
> > > "the streams to retrieve their configuration"
> > >
> > > > camera configuration.
> > > >
> > >
> > > This is a nice and clean way to replace the cumbersome map<Stream *,
> > > StreamConfiguration> used by both streamConfiguration() and
> > > configureStream() and makes it easy to access a configuration from a
> > > Stream *, so it's nice. Though, I don't see how this would help in
> > > handling the "what stream is what" problem at requestComplete() time.
> > > What's missing is the association with a name/id to a configuration,
> > > is this something planned for later or am I missing how this should be
> > > used?
> >
> > This works today, a dumb way for applications to implement this could
> > look like:
> >
> > /* Setup streams */
> > CameraConfiguration config =
> > camera->streamConfiguration({ Stream::Foo(), Stream::Bar() });
> >
> > camera->configureStreams(config);
> >
> > ...
> >
> > camera->requestCompleted.connect(requestComplete);
> >
> > .. star camera etc...
> >
> >
> > void requestComplete(Request *request, const std::map<Stream *, Buffer *> &buffers)
> > {
> > int i = 0;
> > for (stream : config) {
> > if (buffers.find(stream) != buffer.end())
> > printf("Request contains buffer for role position %d\n", i);
> >
> > i++
> > }
> > }
> >
> > More likely the application will create its own
> > std::map<Stream*, ApplicationStreamData> data structure and populate it
> > once using the loop above.
>
> I see. So this aims to replace the id/name based stream identification
> in general.
Yes the id/name idea as we discussed yesterday was a hack idea we picked
to be able to move forward and not the end design of the API. While
working on implementing that I grew sick of how ugly it was and did this
instead :-)
>
> Does this supersedes the idea of having configureStream() assign
> id/names to streams configuration? I sill like the idea of having
> application assign ids to roles, the id is copied to the returned
> stream configuration assigned to a stream, and copied to the stream at
> configureStream() time, so that applications could:
>
> #define STREAM_VF 0
> #define STREAM_STILL 1
>
> CameraConfiguration config = streamConfiguration({STREAM_VF,
> Viewfinder(640x480),
> {STREAM_STILL,
> StillCapture()});
> ...
>
> configureStream(config); // Assign the id in the conf to the
> // stream
>
> ....
>
> void requestComplete(Request *request, const std::map<Stream *, Buffer *> &buffers)
> {
>
> for (auto it : buffers) {
> Stream *s = it.first;
>
> if (s.id == STREAM_VF)
> //display
> if (s.id == STREAM_STILL)
> //save to disk
> }
> }
>
> They could most probably handle that internally with a map or
> something indeed, but this creates a logical connection between the
> intended role and an id applications can control.
Applications can still do that using my previous example, it just needs
to create a std::map<Stream *, AppStreamData>. The ID we use for streams
thru out the library is the Stream *. We could add what you suggests as
a convenience for applications but until we become more mature in the
API this solves the problem and adding things on-top feels wrong at this
time.
Also I don't like the example you have above for streamConfiguration().
It's looks to cumbersome to be nice for applications, but I might be
wrong :-)
> >
> > >
> > > > Signed-off-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
> > > > ---
> > > > include/libcamera/camera.h | 26 ++++++++
> > > > src/libcamera/camera.cpp | 121 +++++++++++++++++++++++++++++++++++++
> > > > 2 files changed, 147 insertions(+)
> > > >
> > > > diff --git a/include/libcamera/camera.h b/include/libcamera/camera.h
> > > > index 0386671c902e55e8..311a51e4070d135c 100644
> > > > --- a/include/libcamera/camera.h
> > > > +++ b/include/libcamera/camera.h
> > > > @@ -14,6 +14,7 @@
> > > >
> > > > #include <libcamera/request.h>
> > > > #include <libcamera/signal.h>
> > > > +#include <libcamera/stream.h>
> > > >
> > > > namespace libcamera {
> > > >
> > > > @@ -24,6 +25,31 @@ class Stream;
> > > > class StreamConfiguration;
> > > > class StreamUsage;
> > > >
> > > > +class CameraConfiguration
> > > > +{
> > > > +public:
> > > > + using iterator = std::vector<Stream *>::iterator;
> > > > + using const_iterator = std::vector<Stream *>::const_iterator;
> > >
> > > Have you considered giving this class iterator traits and implement
> > > methods required for at least, say, ForwardIterator?
> > > http://www.cplusplus.com/reference/iterator/ForwardIterator/
> > >
> > > That would make possible for applications to use STL library functions
> > > that operates on iterators on the class. In example, can you use
> > > range-based for loops on this class?
> >
> > This is a full fledge iterator already that support
> > random_access_iterator_tag. It provides the proper begin() and end()
> > functions which proxies the iterators for order_ which is a std::vector
> > :-)
>
> Do you mean the CameraConfiguration class is a
> randome_access_iterator?
No CameraConfiguration::iterator is.
> I see a lot of methods listed here but not supported by the class
> http://www.cplusplus.com/reference/iterator/RandomAccessIterator/
These methods shall be implemented on the iterator not on the object.
And they are implemented for CameraConfiguration::iterator as that is an
alias for std::vector<Stream *>::iterator, which is a
RandomAccessIterator.
>
> If you forward them to a standard vector, then fine.
>
> Anyway, this is good enough for now most probably.
>
> Thanks
> j
>
> >
> > The STL library functions such as ranged based loops works and are
> > already used in the next patch of this series on this data type.
> >
> > >
> > > > +
> > > > + CameraConfiguration();
> > > > +
> > > > + iterator begin();
> > > > + iterator end();
> > > > + const_iterator begin() const;
> > > > + const_iterator end() const;
> > > > +
> > > > + bool empty() const;
> > > > + std::size_t size() const;
> > > > +
> > > > + Stream *front();
> > > > +
> > > > + StreamConfiguration &operator[](Stream *stream);
> > > > +
> > > > +private:
> > > > + std::vector<Stream *> order_;
> > > > + std::map<Stream *, StreamConfiguration> config_;
> > >
> > > I wonder if keeping the Stream * in two separate places might lead to
> > > issues in keeping the two in sync. But these are privates, so it
> > > should be fine...
> > >
> > > > +};
> > > > +
> > > > class Camera final
> > > > {
> > > > public:
> > > > diff --git a/src/libcamera/camera.cpp b/src/libcamera/camera.cpp
> > > > index 63fde0ffc3d02d6c..16162c524297012f 100644
> > > > --- a/src/libcamera/camera.cpp
> > > > +++ b/src/libcamera/camera.cpp
> > > > @@ -39,6 +39,127 @@ namespace libcamera {
> > > >
> > > > LOG_DECLARE_CATEGORY(Camera)
> > > >
> > > > +/**
> > > > + * \class CameraConfiguration
> > > > + * \brief Hold configuration for streams of the camera that applications
> > > I would drop what's after the "of the camera".
> > > > + * wish to modify and apply.
> > > > + *
> > > > + * The CameraConfiguration is filled with information by the application either
> > > > + * manually or with the streamConfiguration() helper. The helper takes a list
> > > > + * list of usages describing how the application intents to use the camera, the
> > > s/list list/list/
> > > s/intents/intends/
> > > s/use the camera/use the stream/
> > >
> > > > + * application in returns is provided with a default camera configuration it
> > > s/in returns/in return/
> > > > + * can tweak.
> > > > + *
> > > > + * Applications iterates over the CameraConfiguration to discover which streams
> > > s/iterates/iterate/
> > > > + * the camera have selected for its usages and can inspect the configuration
> > > s/the camera have selected for its usage/the camera has associated to a usage/
> > > s/can inspect/can access/
> > > > + * using the operator[].
> > > > + */
> > > > +
> > > > +/**
> > > > + * \typedef CameraConfiguration::iterator
> > > > + * \brief Iterator for the streams in the configuration
> > > > + */
> > > > +
> > > > +/**
> > > > + * \typedef CameraConfiguration::const_iterator
> > > > + * \brief Const iterator for the streams in the configuration
> > > > + */
> > > > +
> > > > +/**
> > > > + * \brief Create an empty camera configuration
> > > > + */
> > > > +CameraConfiguration::CameraConfiguration()
> > > > + : order_({}), config_({})
> > > > +{
> > > > +}
> > > > +
> > > > +/**
> > > > + * \brief Retrieve an iterator to the first element of the streams
> > > > + *
> > >
> > > The standard iterator documentation for begin reports:
> > > "Returns an iterator pointing to the first element in the sequence"
> > >
> > > Could we match this?
> > >
> > > > + * \return An iterator to the first stream
> > > > + */
> > > > +std::vector<Stream *>::iterator CameraConfiguration::begin()
> > > > +{
> > > > + return order_.begin();
> > > > +}
> > > > +
> > > > +/**
> > > > + * \brief Retrieve an iterator to the end of the streams
> > >
> > > Same as per 'begin()':
> > >
> > > "Returns an iterator pointing to the past-the-end element in the sequence"
> > >
> > > > + *
> > > > + * \return An iterator to the element following the last stream
> > > > + */
> > > > +std::vector<Stream *>::iterator CameraConfiguration::end()
> > > > +{
> > > > + return order_.end();
> > > > +}
> > > > +
> > > > +/**
> > > > + * \brief Retrieve an iterator to the first element of the streams
> > > > + *
> > > > + * \return An iterator to the first stream
> > > > + */
> > > > +std::vector<Stream *>::const_iterator CameraConfiguration::begin() const
> > > > +{
> > > > + return order_.begin();
> > > > +}
> > > > +
> > > > +/**
> > > > + * \brief Retrieve an iterator to the end of the streams
> > > > + *
> > > > + * \return An iterator to the element following the last stream
> > > > + */
> > > > +std::vector<Stream *>::const_iterator CameraConfiguration::end() const
> > > > +{
> > > > + return order_.end();
> > > > +}
> > > > +
> > > > +/**
> > > > + * \brief Checks whether the camera configuration is empty
> > > > + *
> > > > + * \return True if the configuration is empty
> > > > + */
> > > > +bool CameraConfiguration::empty() const
> > > > +{
> > > > + return order_.empty();
> > > > +}
> > > > +
> > > > +/**
> > > > + * \brief Check the number of stream configurations
> > > > + *
> > > > + * \return Number of stream configurations
> > > > + */
> > > > +std::size_t CameraConfiguration::size() const
> > > > +{
> > > > + return order_.size();
> > > > +}
> > > > +
> > > > +/**
> > > > + * \brief Access the first stream in the configuration
> > > > + *
> > > > + * \return The first stream in the configuration
> > > > + */
> > > > +Stream *CameraConfiguration::front()
> > > > +{
> > > > + return order_.front();
> > > > +}
> > > > +
> > > > +/**
> > > > + * \brief Retrieve a reference to a stream configuration
> > > > + * \param[in] stream Stream to retrieve configuration for
> > > > + *
> > > > + * If the camera configuration do not yet contain configuration for the
> > >
> > > contain a configuration
> > >
> > > > + * requested stream an empty stream configuration is created and returned.
> > >
> > > empty one
> > >
> > > > + *
> > > > + * \return Configuration for the stream
> > >
> > > The configuration
> > >
> > > > + */
> > > > +StreamConfiguration &CameraConfiguration::operator[](Stream *stream)
> > > > +{
> > > > + if (config_.find(stream) == config_.end())
> > > > + order_.push_back(stream);
> > > > +
> > > > + return config_[stream];
> > > > +}
> > > > +
> > >
> > > I don't know how welcome would the idea of making of this class a
> > > full-fledged iterator, but I think increment, decrement and access by
> > > integer index should be implemented to make it more useful. Have you
> > > considered that?
> >
> > As stated above it is already implemented. Well not integer indexed as
> > the whole idea if this object is to make it Stream* indexed but preserve
> > the insertion order when iterating over it to allow mapping stream
> > usages to stream configurations.
> >
> > >
> > > Thanks
> > > j
> > >
> > > > /**
> > > > * \class Camera
> > > > * \brief Camera device
> > > > --
> > > > 2.21.0
> > > >
> > > > _______________________________________________
> > > > libcamera-devel mailing list
> > > > libcamera-devel at lists.libcamera.org
> > > > https://lists.libcamera.org/listinfo/libcamera-devel
> >
> >
> >
> > --
> > Regards,
> > Niklas Söderlund
--
Regards,
Niklas Söderlund
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