blob: 10212ac81648050ec9a12abc0fa1e2a621c00fad [file] [log] [blame]
* 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.
#include <memory>
#include <string>
#include <vector>
#include "absl/algorithm/container.h"
#include "api/array_view.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 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 {
std::vector<SdpVideoFormat> GetSupportedFormats() const override {
return GetSupportedFormatsInternal<Ts...>();
std::unique_ptr<VideoEncoder> CreateVideoEncoder(
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( Remove FuzzyMatchSdpVideoFormat
absl::optional<SdpVideoFormat> matched =
FuzzyMatchSdpVideoFormat(GetSupportedFormats(), format);
return CreateVideoEncoderInternal<Ts...>(matched.value_or(format));
CodecSupport QueryCodecSupport(
const SdpVideoFormat& format,
absl::optional<std::string> scalability_mode) const override {
return QueryCodecSupportInternal<Ts...>(format, scalability_mode);
bool IsFormatInList(
const SdpVideoFormat& format,
rtc::ArrayView<const SdpVideoFormat> supported_formats) const {
return absl::c_any_of(
supported_formats, [&](const SdpVideoFormat& supported_format) {
return == &&
supported_format.parameters == format.parameters;
template <typename V>
bool IsScalabilityModeSupported(
const absl::optional<std::string>& scalability_mode_string) const {
if (!scalability_mode_string.has_value()) {
return true;
absl::optional<ScalabilityMode> scalability_mode =
return scalability_mode.has_value() &&
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)) {
return supported_formats;
template <typename V, typename... Vs>
std::unique_ptr<VideoEncoder> CreateVideoEncoderInternal(
const SdpVideoFormat& format) {
if (IsFormatInList(format, V::SupportedFormats())) {
return V::CreateEncoder(format);
if constexpr (sizeof...(Vs) > 0) {
return CreateVideoEncoderInternal<Vs...>(format);
return nullptr;
template <typename V, typename... Vs>
CodecSupport QueryCodecSupportInternal(
const SdpVideoFormat& format,
const absl::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