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// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef MEDIA_CAPTURE_CONTENT_CAPTURE_RESOLUTION_CHOOSER_H_
#define MEDIA_CAPTURE_CONTENT_CAPTURE_RESOLUTION_CHOOSER_H_
#include <vector>
#include "media/base/video_capture_types.h"
#include "media/capture/capture_export.h"
#include "ui/gfx/geometry/size.h"
namespace media {
// Encapsulates the logic that determines the capture frame resolution based on:
// 1. The configured maximum frame resolution and resolution change policy.
// 2. Changes to resolution of the source content.
// 3. Changes to the (externally-computed) target data volume, provided in
// terms of the number of pixels in the frame.
//
// CaptureResolutionChooser always computes capture sizes less than the maximum
// frame size, and adheres to the configured resolution change policy. Within
// those hard limits, the capture size is computed to be as close to the
// targeted frame area as possible.
//
// In variable-resolution use cases, the capture sizes are "snapped" to a small
// (i.e., usually less than a dozen) set of possibilities. This is to prevent
// the end-to-end system from having to deal with rapidly-changing video frame
// resolutions that results from providing a fine-grained range of values. The
// possibile snapped frame sizes are computed relative to the resolution of the
// source content: They are the same or smaller in size, and are of the same
// aspect ratio.
class CAPTURE_EXPORT CaptureResolutionChooser {
public:
// media::ResolutionChangePolicy determines whether the variable frame
// resolutions being computed must adhere to a fixed aspect ratio or not, or
// that there must only be a single fixed resolution.
CaptureResolutionChooser(const gfx::Size& max_frame_size,
ResolutionChangePolicy resolution_change_policy);
~CaptureResolutionChooser();
// Returns the current capture frame resolution to use.
gfx::Size capture_size() const { return capture_size_; }
// Updates the capture size based on a change in the resolution of the source
// content.
void SetSourceSize(const gfx::Size& source_size);
// Updates the capture size to target the given frame area, in terms of
// gfx::Size::GetArea(). The initial target frame area is the maximum int
// (i.e., always target the source size).
void SetTargetFrameArea(int area);
// Search functions to, given a frame |area|, return the nearest snapped frame
// size, or N size steps up/down. Snapped frame sizes are based on the
// current source size.
gfx::Size FindNearestFrameSize(int area) const;
gfx::Size FindLargerFrameSize(int area, int num_steps_up) const;
gfx::Size FindSmallerFrameSize(int area, int num_steps_down) const;
private:
// Called after any update that requires |capture_size_| be re-computed.
void RecomputeCaptureSize();
// Recomputes the |snapped_sizes_| cache.
void UpdateSnappedFrameSizes(const gfx::Size& constrained_size);
// Hard constraints.
const gfx::Size max_frame_size_;
const gfx::Size min_frame_size_; // Computed from the ctor arguments.
// Specifies the set of heuristics to use.
const ResolutionChangePolicy resolution_change_policy_;
// |capture_size_| will be computed such that its area is as close to this
// value as possible.
int target_area_;
// The current computed capture frame resolution.
gfx::Size capture_size_;
// Cache of the set of possible values |capture_size_| can have, in order from
// smallest to largest. This is recomputed whenever UpdateSnappedFrameSizes()
// is called.
std::vector<gfx::Size> snapped_sizes_;
};
} // namespace media
#endif // MEDIA_CAPTURE_CONTENT_CAPTURE_RESOLUTION_CHOOSER_H_