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/*
* Copyright (c) 2022 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#ifndef API_VIDEO_CODECS_VIDEO_ENCODER_FACTORY_TEMPLATE_H_
#define API_VIDEO_CODECS_VIDEO_ENCODER_FACTORY_TEMPLATE_H_
#include <memory>
#include <optional>
#include <string>
#include <vector>
#include "absl/algorithm/container.h"
#include "api/array_view.h"
#include "api/environment/environment.h"
#include "api/video_codecs/scalability_mode.h"
#include "api/video_codecs/sdp_video_format.h"
#include "api/video_codecs/video_encoder.h"
#include "api/video_codecs/video_encoder_factory.h"
#include "modules/video_coding/svc/scalability_mode_util.h"
namespace webrtc {
// The VideoEncoderFactoryTemplate supports encoders implementations given as
// template arguments.
//
// To include an encoder in the factory it requires three static members
// functions to be defined:
//
// // Returns the supported SdpVideoFormats this encoder can produce.
// static std::vector<SdpVideoFormat> SupportedFormats();
//
// // Creates an encoder instance for the given format.
// static std::unique_ptr<VideoEncoder>
// CreateEncoder(const Environment& env,
// const SdpVideoFormat& format);
//
// // Returns true if the encoder supports the given scalability mode.
// static bool
// IsScalabilityModeSupported(ScalabilityMode scalability_mode);
//
// Note that the order of the template arguments matter as the factory will
// query/return the first encoder implementation supporting the given
// SdpVideoFormat.
template <typename... Ts>
class VideoEncoderFactoryTemplate : public VideoEncoderFactory {
public:
std::vector<SdpVideoFormat> GetSupportedFormats() const override {
return GetSupportedFormatsInternal<Ts...>();
}
std::unique_ptr<VideoEncoder> Create(const Environment& env,
const SdpVideoFormat& format) override {
// We fuzzy match the specified format for both valid and not so valid
// reasons. The valid reason is that there are many standardized codec
// specific fmtp parameters that have not been implemented, and in those
// cases we should not fail to instantiate an encoder just because we don't
// recognize the parameter. The not so valid reason is that we have started
// adding parameters completely unrelated to the SDP to the SdpVideoFormat.
// TODO: bugs.webrtc.org/13868 - Remove FuzzyMatchSdpVideoFormat
std::optional<SdpVideoFormat> matched =
FuzzyMatchSdpVideoFormat(GetSupportedFormats(), format);
return CreateInternal<Ts...>(env, matched.value_or(format));
}
CodecSupport QueryCodecSupport(
const SdpVideoFormat& format,
std::optional<std::string> scalability_mode) const override {
return QueryCodecSupportInternal<Ts...>(format, scalability_mode);
}
private:
bool IsFormatInList(const SdpVideoFormat& format,
ArrayView<const SdpVideoFormat> supported_formats) const {
return absl::c_any_of(
supported_formats, [&](const SdpVideoFormat& supported_format) {
return supported_format.name == format.name &&
supported_format.parameters == format.parameters;
});
}
template <typename V>
bool IsScalabilityModeSupported(
const std::optional<std::string>& scalability_mode_string) const {
if (!scalability_mode_string.has_value()) {
return true;
}
std::optional<ScalabilityMode> scalability_mode =
ScalabilityModeFromString(*scalability_mode_string);
return scalability_mode.has_value() &&
V::IsScalabilityModeSupported(*scalability_mode);
}
template <typename V, typename... Vs>
std::vector<SdpVideoFormat> GetSupportedFormatsInternal() const {
auto supported_formats = V::SupportedFormats();
if constexpr (sizeof...(Vs) > 0) {
// Supported formats may overlap between implementations, so duplicates
// should be filtered out.
for (const auto& other_format : GetSupportedFormatsInternal<Vs...>()) {
if (!IsFormatInList(other_format, supported_formats)) {
supported_formats.push_back(other_format);
}
}
}
return supported_formats;
}
template <typename V, typename... Vs>
std::unique_ptr<VideoEncoder> CreateInternal(const Environment& env,
const SdpVideoFormat& format) {
if (IsFormatInList(format, V::SupportedFormats())) {
return V::CreateEncoder(env, format);
}
if constexpr (sizeof...(Vs) > 0) {
return CreateInternal<Vs...>(env, format);
}
return nullptr;
}
template <typename V, typename... Vs>
CodecSupport QueryCodecSupportInternal(
const SdpVideoFormat& format,
const std::optional<std::string>& scalability_mode) const {
if (IsFormatInList(format, V::SupportedFormats())) {
return {.is_supported = IsScalabilityModeSupported<V>(scalability_mode)};
}
if constexpr (sizeof...(Vs) > 0) {
return QueryCodecSupportInternal<Vs...>(format, scalability_mode);
}
return {.is_supported = false};
}
};
} // namespace webrtc
#endif // API_VIDEO_CODECS_VIDEO_ENCODER_FACTORY_TEMPLATE_H_
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