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Diffstat (limited to 'third_party/libwebrtc/api/audio_codecs/audio_encoder_factory_template.h')
| -rw-r--r-- | third_party/libwebrtc/api/audio_codecs/audio_encoder_factory_template.h | 163 |
1 files changed, 163 insertions, 0 deletions
diff --git a/third_party/libwebrtc/api/audio_codecs/audio_encoder_factory_template.h b/third_party/libwebrtc/api/audio_codecs/audio_encoder_factory_template.h new file mode 100644 index 0000000000..8a70ba2268 --- /dev/null +++ b/third_party/libwebrtc/api/audio_codecs/audio_encoder_factory_template.h @@ -0,0 +1,163 @@ +/* + * Copyright (c) 2017 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_AUDIO_CODECS_AUDIO_ENCODER_FACTORY_TEMPLATE_H_ +#define API_AUDIO_CODECS_AUDIO_ENCODER_FACTORY_TEMPLATE_H_ + +#include <memory> +#include <vector> + +#include "api/audio_codecs/audio_encoder_factory.h" +#include "api/field_trials_view.h" +#include "api/make_ref_counted.h" +#include "api/scoped_refptr.h" + +namespace webrtc { + +namespace audio_encoder_factory_template_impl { + +template <typename... Ts> +struct Helper; + +// Base case: 0 template parameters. +template <> +struct Helper<> { + static void AppendSupportedEncoders(std::vector<AudioCodecSpec>* specs) {} + static absl::optional<AudioCodecInfo> QueryAudioEncoder( + const SdpAudioFormat& format) { + return absl::nullopt; + } + static std::unique_ptr<AudioEncoder> MakeAudioEncoder( + int payload_type, + const SdpAudioFormat& format, + absl::optional<AudioCodecPairId> codec_pair_id, + const FieldTrialsView* field_trials) { + return nullptr; + } +}; + +// Inductive case: Called with n + 1 template parameters; calls subroutines +// with n template parameters. +template <typename T, typename... Ts> +struct Helper<T, Ts...> { + static void AppendSupportedEncoders(std::vector<AudioCodecSpec>* specs) { + T::AppendSupportedEncoders(specs); + Helper<Ts...>::AppendSupportedEncoders(specs); + } + static absl::optional<AudioCodecInfo> QueryAudioEncoder( + const SdpAudioFormat& format) { + auto opt_config = T::SdpToConfig(format); + static_assert(std::is_same<decltype(opt_config), + absl::optional<typename T::Config>>::value, + "T::SdpToConfig() must return a value of type " + "absl::optional<T::Config>"); + return opt_config ? absl::optional<AudioCodecInfo>( + T::QueryAudioEncoder(*opt_config)) + : Helper<Ts...>::QueryAudioEncoder(format); + } + static std::unique_ptr<AudioEncoder> MakeAudioEncoder( + int payload_type, + const SdpAudioFormat& format, + absl::optional<AudioCodecPairId> codec_pair_id, + const FieldTrialsView* field_trials) { + auto opt_config = T::SdpToConfig(format); + if (opt_config) { + return T::MakeAudioEncoder(*opt_config, payload_type, codec_pair_id); + } else { + return Helper<Ts...>::MakeAudioEncoder(payload_type, format, + codec_pair_id, field_trials); + } + } +}; + +template <typename... Ts> +class AudioEncoderFactoryT : public AudioEncoderFactory { + public: + explicit AudioEncoderFactoryT(const FieldTrialsView* field_trials) { + field_trials_ = field_trials; + } + + std::vector<AudioCodecSpec> GetSupportedEncoders() override { + std::vector<AudioCodecSpec> specs; + Helper<Ts...>::AppendSupportedEncoders(&specs); + return specs; + } + + absl::optional<AudioCodecInfo> QueryAudioEncoder( + const SdpAudioFormat& format) override { + return Helper<Ts...>::QueryAudioEncoder(format); + } + + std::unique_ptr<AudioEncoder> MakeAudioEncoder( + int payload_type, + const SdpAudioFormat& format, + absl::optional<AudioCodecPairId> codec_pair_id) override { + return Helper<Ts...>::MakeAudioEncoder(payload_type, format, codec_pair_id, + field_trials_); + } + + const FieldTrialsView* field_trials_; +}; + +} // namespace audio_encoder_factory_template_impl + +// Make an AudioEncoderFactory that can create instances of the given encoders. +// +// Each encoder type is given as a template argument to the function; it should +// be a struct with the following static member functions: +// +// // Converts `audio_format` to a ConfigType instance. Returns an empty +// // optional if `audio_format` doesn't correctly specify an encoder of our +// // type. +// absl::optional<ConfigType> SdpToConfig(const SdpAudioFormat& audio_format); +// +// // Appends zero or more AudioCodecSpecs to the list that will be returned +// // by AudioEncoderFactory::GetSupportedEncoders(). +// void AppendSupportedEncoders(std::vector<AudioCodecSpec>* specs); +// +// // Returns information about how this format would be encoded. Used to +// // implement AudioEncoderFactory::QueryAudioEncoder(). +// AudioCodecInfo QueryAudioEncoder(const ConfigType& config); +// +// // Creates an AudioEncoder for the specified format. Used to implement +// // AudioEncoderFactory::MakeAudioEncoder(). +// std::unique_ptr<AudioDecoder> MakeAudioEncoder( +// const ConfigType& config, +// int payload_type, +// absl::optional<AudioCodecPairId> codec_pair_id); +// +// ConfigType should be a type that encapsulates all the settings needed to +// create an AudioEncoder. T::Config (where T is the encoder struct) should +// either be the config type, or an alias for it. +// +// Whenever it tries to do something, the new factory will try each of the +// encoders in the order they were specified in the template argument list, +// stopping at the first one that claims to be able to do the job. +// +// TODO(kwiberg): Point at CreateBuiltinAudioEncoderFactory() for an example of +// how it is used. +template <typename... Ts> +rtc::scoped_refptr<AudioEncoderFactory> CreateAudioEncoderFactory( + const FieldTrialsView* field_trials = nullptr) { + // There's no technical reason we couldn't allow zero template parameters, + // but such a factory couldn't create any encoders, and callers can do this + // by mistake by simply forgetting the <> altogether. So we forbid it in + // order to prevent caller foot-shooting. + static_assert(sizeof...(Ts) >= 1, + "Caller must give at least one template parameter"); + + return rtc::make_ref_counted< + audio_encoder_factory_template_impl::AudioEncoderFactoryT<Ts...>>( + field_trials); +} + +} // namespace webrtc + +#endif // API_AUDIO_CODECS_AUDIO_ENCODER_FACTORY_TEMPLATE_H_ |