VideoToolBox decoder/encoder for MacOS & iOS (#19)

* VideoDecoderFactory wrapper

* wip

* fix compilation

* add notes

* upgrade webrtc version

webrtc-sys/src/video_decoder_factory.cpp

@@ -0,0 +1,46 @@
+#include "livekit/video_decoder_factory.h"
+
+#include "api/video_codecs/builtin_video_decoder_factory.h"
+#include "api/video_codecs/builtin_video_encoder_factory.h"
+#include "api/video_codecs/sdp_video_format.h"
+#include "livekit/objc_video_factory.h"
+#include "media/base/media_constants.h"
+#include "rtc_base/logging.h"
+
+namespace livekit {
+
+VideoDecoderFactory::VideoDecoderFactory() {
+  factories_.push_back(webrtc::CreateBuiltinVideoDecoderFactory());
+
+#ifdef __APPLE__
+  factories_.push_back(livekit::CreateObjCVideoDecoderFactory());
+#endif
+
+  // TODO(theomonnom): Add other HW decoders here
+}
+
+std::vector<webrtc::SdpVideoFormat> VideoDecoderFactory::GetSupportedFormats()
+    const {
+  std::vector<webrtc::SdpVideoFormat> formats;
+  for (const auto& factory : factories_) {
+    auto supported_formats = factory->GetSupportedFormats();
+    formats.insert(formats.end(), supported_formats.begin(),
+                   supported_formats.end());
+  }
+  return formats;
+}
+
+std::unique_ptr<webrtc::VideoDecoder> VideoDecoderFactory::CreateVideoDecoder(
+    const webrtc::SdpVideoFormat& format) {
+  for (const auto& factory : factories_) {
+    for (const auto& supported_format : factory->GetSupportedFormats()) {
+      if (supported_format.IsSameCodec(format))
+        return factory->CreateVideoDecoder(format);
+    }
+  }
+
+  RTC_LOG(LS_ERROR) << "No VideoDecoder found for " << format.name;
+  return nullptr;
+}
+
+}  // namespace livekit