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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_DECODER_FACTORY_TEMPLATE_H_
#define API_VIDEO_CODECS_VIDEO_DECODER_FACTORY_TEMPLATE_H_
#include <memory>
#include <type_traits>
#include <vector>
#include "absl/algorithm/container.h"
#include "api/array_view.h"
#include "api/environment/environment.h"
#include "api/video_codecs/sdp_video_format.h"
#include "api/video_codecs/video_decoder.h"
#include "api/video_codecs/video_decoder_factory.h"
namespace webrtc {
// The VideoDecoderFactoryTemplate supports decoder implementations given as
// template arguments.
//
// To include a decoder in the factory it requires two static members
// functions to be defined:
//
// // Returns the supported SdpVideoFormats this decoder can decode.
// static std::vector<SdpVideoFormat> SupportedFormats();
//
// // Creates a decoder instance for the given format.
// static std::unique_ptr<VideoDecoder>
// CreateDecoder(const Environment& env,
// const SdpVideoFormat& format);
//
// Note that the order of the template arguments matter as the factory will
// return the first decoder implementation supporting the given SdpVideoFormat.
template <typename... Ts>
class VideoDecoderFactoryTemplate : public VideoDecoderFactory {
public:
std::vector<SdpVideoFormat> GetSupportedFormats() const override {
return GetSupportedFormatsInternal<Ts...>();
}
std::unique_ptr<VideoDecoder> Create(const Environment& env,
const SdpVideoFormat& format) override {
return CreateVideoDecoderInternal<Ts...>(env, format);
}
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, 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<VideoDecoder> CreateVideoDecoderInternal(
const Environment& env,
const SdpVideoFormat& format) {
if (IsFormatInList(format, V::SupportedFormats())) {
if constexpr (std::is_invocable_r_v<std::unique_ptr<VideoDecoder>,
decltype(V::CreateDecoder),
const Environment&,
const SdpVideoFormat&>) {
return V::CreateDecoder(env, format);
} else {
return V::CreateDecoder(format);
}
}
if constexpr (sizeof...(Vs) > 0) {
return CreateVideoDecoderInternal<Vs...>(env, format);
}
return nullptr;
}
};
} // namespace webrtc
#endif // API_VIDEO_CODECS_VIDEO_DECODER_FACTORY_TEMPLATE_H_
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