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// Copyright 2020 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.
#include "cast/streaming/capture_recommendations.h"
#include <algorithm>
#include <utility>
#include "cast/streaming/answer_messages.h"
#include "util/osp_logging.h"
namespace openscreen {
namespace cast {
namespace capture_recommendations {
namespace {
bool DoubleEquals(double a, double b) {
// Choice of epsilon for double comparison allows for proper comparison
// for both aspect ratios and frame rates. For frame rates, it is based on the
// broadcast rate of 29.97fps, which is actually 29.976. For aspect ratios, it
// allows for a one-pixel difference at a 4K resolution, we want it to be
// relatively high to avoid false negative comparison results.
const double kEpsilon = .0001;
return std::abs(a - b) < kEpsilon;
}
void ApplyDisplay(const DisplayDescription& description,
Recommendations* recommendations) {
recommendations->video.supports_scaling =
(description.aspect_ratio_constraint &&
(description.aspect_ratio_constraint.value() ==
AspectRatioConstraint::kVariable));
// We should never exceed the display's resolution, since it will always
// force scaling.
if (description.dimensions) {
const double frame_rate =
static_cast<double>(description.dimensions->frame_rate);
recommendations->video.maximum =
Resolution{description.dimensions->width,
description.dimensions->height, frame_rate};
recommendations->video.bit_rate_limits.maximum =
recommendations->video.maximum.effective_bit_rate();
recommendations->video.minimum.set_minimum(recommendations->video.maximum);
}
// If the receiver gives us an aspect ratio that doesn't match the display
// resolution they give us, the behavior is undefined from the spec.
// Here we prioritize the aspect ratio, and the receiver can scale the frame
// as they wish.
double aspect_ratio = 0.0;
if (description.aspect_ratio) {
aspect_ratio = static_cast<double>(description.aspect_ratio->width) /
description.aspect_ratio->height;
#if OSP_DCHECK_IS_ON()
if (description.dimensions) {
const double from_dims =
static_cast<double>(description.dimensions->width) /
description.dimensions->height;
if (!DoubleEquals(from_dims, aspect_ratio)) {
OSP_DLOG_WARN << "Received mismatched aspect ratio from the receiver.";
}
}
#endif
recommendations->video.maximum.width =
recommendations->video.maximum.height * aspect_ratio;
} else if (description.dimensions) {
aspect_ratio = static_cast<double>(description.dimensions->width) /
description.dimensions->height;
} else {
return;
}
recommendations->video.minimum.width =
recommendations->video.minimum.height * aspect_ratio;
}
Resolution ToResolution(const Dimensions& dims) {
return {dims.width, dims.height, static_cast<double>(dims.frame_rate)};
}
void ApplyConstraints(const Constraints& constraints,
Recommendations* recommendations) {
// Audio has no fields in the display description, so we can safely
// ignore the current recommendations when setting values here.
if (constraints.audio.max_delay.has_value()) {
recommendations->audio.max_delay = constraints.audio.max_delay.value();
}
recommendations->audio.max_channels = constraints.audio.max_channels;
recommendations->audio.max_sample_rate = constraints.audio.max_sample_rate;
recommendations->audio.bit_rate_limits = BitRateLimits{
std::max(constraints.audio.min_bit_rate, kDefaultAudioMinBitRate),
std::max(constraints.audio.max_bit_rate, kDefaultAudioMinBitRate)};
// With video, we take the intersection of values of the constraints and
// the display description.
if (constraints.video.max_delay.has_value()) {
recommendations->video.max_delay = constraints.video.max_delay.value();
}
if (constraints.video.max_pixels_per_second.has_value()) {
recommendations->video.max_pixels_per_second =
constraints.video.max_pixels_per_second.value();
}
recommendations->video.bit_rate_limits =
BitRateLimits{std::max(constraints.video.min_bit_rate,
recommendations->video.bit_rate_limits.minimum),
std::min(constraints.video.max_bit_rate,
recommendations->video.bit_rate_limits.maximum)};
Resolution max = ToResolution(constraints.video.max_dimensions);
if (max <= kDefaultMinResolution) {
recommendations->video.maximum = kDefaultMinResolution;
} else if (max < recommendations->video.maximum) {
recommendations->video.maximum = std::move(max);
}
// Implicit else: maximum = kDefaultMaxResolution.
if (constraints.video.min_dimensions) {
Resolution min = ToResolution(constraints.video.min_dimensions.value());
if (kDefaultMinResolution < min) {
recommendations->video.minimum = std::move(min);
}
}
}
} // namespace
bool BitRateLimits::operator==(const BitRateLimits& other) const {
return std::tie(minimum, maximum) == std::tie(other.minimum, other.maximum);
}
bool Audio::operator==(const Audio& other) const {
return std::tie(bit_rate_limits, max_delay, max_channels, max_sample_rate) ==
std::tie(other.bit_rate_limits, other.max_delay, other.max_channels,
other.max_sample_rate);
}
bool Resolution::operator==(const Resolution& other) const {
return (std::tie(width, height) == std::tie(other.width, other.height)) &&
DoubleEquals(frame_rate, other.frame_rate);
}
bool Resolution::operator<(const Resolution& other) const {
return effective_bit_rate() < other.effective_bit_rate();
}
bool Resolution::operator<=(const Resolution& other) const {
return (*this == other) || (*this < other);
}
void Resolution::set_minimum(const Resolution& other) {
if (other < *this) {
*this = other;
}
}
bool Video::operator==(const Video& other) const {
return std::tie(bit_rate_limits, minimum, maximum, supports_scaling,
max_delay, max_pixels_per_second) ==
std::tie(other.bit_rate_limits, other.minimum, other.maximum,
other.supports_scaling, other.max_delay,
other.max_pixels_per_second);
}
bool Recommendations::operator==(const Recommendations& other) const {
return std::tie(audio, video) == std::tie(other.audio, other.video);
}
Recommendations GetRecommendations(const Answer& answer) {
Recommendations recommendations;
if (answer.display.has_value() && answer.display->IsValid()) {
ApplyDisplay(answer.display.value(), &recommendations);
}
if (answer.constraints.has_value() && answer.constraints->IsValid()) {
ApplyConstraints(answer.constraints.value(), &recommendations);
}
return recommendations;
}
} // namespace capture_recommendations
} // namespace cast
} // namespace openscreen
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