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/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
* Copyright (C) 2019, Google Inc.
*
* stream.cpp - Video stream for a Camera
*/
#include <libcamera/stream.h>
#include <iomanip>
#include <sstream>
/**
* \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 {
/**
* \struct StreamConfiguration
* \brief Configuration parameters for a stream
*
* The StreamConfiguration structure models all information which can be
* configured for a single video stream.
*/
/**
* \var StreamConfiguration::size
* \brief Stream size in pixels
*/
/**
* \var StreamConfiguration::pixelFormat
* \brief Stream pixel format
*
* This is a little endian four character code representation of the pixel
* format described in V4L2 using the V4L2_PIX_FMT_* definitions.
*/
/**
* \var StreamConfiguration::bufferCount
* \brief Requested number of buffers to allocate for the stream
*/
/**
* \brief Assemble and return a string describing the configuration
*
* \return A string describing the StreamConfiguration
*/
std::string StreamConfiguration::toString() const
{
std::stringstream ss;
ss.fill(0);
ss << size.toString() << "-0x" << std::hex << std::setw(8)
<< pixelFormat;
return ss.str();
}
/**
* \class StreamUsage
* \brief Stream usage information
*
* The StreamUsage class describes how an application intends to use a stream.
* Usages are specified by applications and passed to cameras, that then select
* the most appropriate streams and their default configurations.
*/
/**
* \enum StreamUsage::Role
* \brief Identify the role a stream is intended to play
* \var StreamUsage::StillCapture
* The stream is intended to capture high-resolution, high-quality still images
* with low frame rate. The captured frames may be exposed with flash.
* \var StreamUsage::VideoRecording
* The stream is intended to capture video for the purpose of recording or
* streaming. The video stream may produce a high frame rate and may be
* enhanced with video stabilization.
* \var StreamUsage::Viewfinder
* The stream is intended to capture video for the purpose of display on the
* local screen. The StreamUsage includes the desired resolution. Trade-offs
* between quality and usage of system resources are acceptable.
*/
/**
* \fn StreamUsage::role()
* \brief Retrieve the stream role
* \return The stream role
*/
/**
* \fn StreamUsage::size()
* \brief Retrieve desired size
* \return The desired size
*/
/**
* \brief Create a stream usage
* \param[in] role Stream role
*/
StreamUsage::StreamUsage(Role role)
: role_(role)
{
}
/**
* \brief Create a stream usage with a desired size
* \param[in] role Stream role
* \param[in] size The desired size
*/
StreamUsage::StreamUsage(Role role, const Size &size)
: role_(role), size_(size)
{
}
/**
* \class Stream
* \brief Video stream for a camera
*
* The Stream class models all static information which are associated with a
* single video stream. Streams are exposed by the Camera object they belong to.
*
* Cameras may supply more than one stream from the same video 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.
*/
/**
* \class Stream::StillCapture
* \brief Describe a still capture usage
*/
Stream::StillCapture::StillCapture()
: StreamUsage(Role::StillCapture)
{
}
/**
* \class Stream::VideoRecording
* \brief Describe a video recording usage
*/
Stream::VideoRecording::VideoRecording()
: StreamUsage(Role::VideoRecording)
{
}
/**
* \class Stream::Viewfinder
* \brief Describe a viewfinder usage
*/
/**
* \brief Create a viewfinder usage with a desired dimension
* \param[in] width The desired viewfinder width
* \param[in] height The desired viewfinder height
*/
Stream::Viewfinder::Viewfinder(int width, int height)
: StreamUsage(Role::Viewfinder, Size(width, height))
{
}
/**
* \brief Construct a stream with default parameters
*/
Stream::Stream()
{
}
/**
* \fn Stream::bufferPool()
* \brief Retrieve the buffer pool for the stream
*
* The buffer pool handles the buffers used to capture frames at the output of
* the stream. It is initially created empty and shall be populated with
* buffers before being used.
*
* \return A reference to the buffer pool
*/
/**
* \fn Stream::configuration()
* \brief Retrieve the active configuration of the stream
* \return The active configuration of the stream
*/
/**
* \var Stream::bufferPool_
* \brief The pool of buffers associated with the stream
*
* The stream buffer pool is populated by the Camera class after a succesfull
* stream configuration.
*/
/**
* \var Stream::configuration_
* \brief The stream configuration
*
* The configuration for the stream is set by any successful call to
* Camera::configureStreams() that includes the stream, and remains valid until
* the next call to Camera::configureStreams() regardless of if it includes the
* stream.
*/
} /* namespace libcamera */
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