api/video_codecs: Add scalability mode helper functions.

Bug: webrtc:13960
Change-Id: I8c86e440223929594aec06e8b32b4bbe73546a94
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/273303
Reviewed-by: Rasmus Brandt <brandtr@webrtc.org>
Reviewed-by: Florent Castelli <orphis@webrtc.org>
Commit-Queue: Åsa Persson <asapersson@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#37994}

api/video_codecs/BUILD.gn

@@ -25,6 +25,19 @@ rtc_source_set("scalability_mode") {
   absl_deps = [ "//third_party/abseil-cpp/absl/strings" ]
 }
 
+rtc_source_set("scalability_mode_helper") {
+  visibility = [ "*" ]
+  sources = [
+    "scalability_mode_helper.cc",
+    "scalability_mode_helper.h",
+  ]
+  deps = [ "../../modules/video_coding/svc:scalability_mode_util" ]
+  absl_deps = [
+    "//third_party/abseil-cpp/absl/strings",
+    "//third_party/abseil-cpp/absl/types:optional",
+  ]
+}
+
 rtc_library("video_codecs_api") {
   visibility = [ "*" ]
   sources = [

api/video_codecs/scalability_mode_helper.cc

@@ -0,0 +1,37 @@
+/*
+ *  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 "api/video_codecs/scalability_mode_helper.h"
+
+#include "modules/video_coding/svc/scalability_mode_util.h"
+
+namespace webrtc {
+
+absl::optional<int> ScalabilityModeStringToNumSpatialLayers(
+    absl::string_view scalability_mode_string) {
+  absl::optional<ScalabilityMode> scalability_mode =
+      ScalabilityModeFromString(scalability_mode_string);
+  if (!scalability_mode.has_value()) {
+    return absl::nullopt;
+  }
+  return ScalabilityModeToNumSpatialLayers(*scalability_mode);
+}
+
+absl::optional<int> ScalabilityModeStringToNumTemporalLayers(
+    absl::string_view scalability_mode_string) {
+  absl::optional<ScalabilityMode> scalability_mode =
+      ScalabilityModeFromString(scalability_mode_string);
+  if (!scalability_mode.has_value()) {
+    return absl::nullopt;
+  }
+  return ScalabilityModeToNumTemporalLayers(*scalability_mode);
+}
+
+}  // namespace webrtc

api/video_codecs/scalability_mode_helper.h

@@ -0,0 +1,31 @@
+/*
+ *  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_SCALABILITY_MODE_HELPER_H_
+#define API_VIDEO_CODECS_SCALABILITY_MODE_HELPER_H_
+
+#include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
+
+namespace webrtc {
+
+// Returns the number of spatial layers from the `scalability_mode_string`
+// or nullopt if the given mode is unknown.
+absl::optional<int> ScalabilityModeStringToNumSpatialLayers(
+    absl::string_view scalability_mode_string);
+
+// Returns the number of temporal layers from the `scalability_mode_string`
+// or nullopt if the given mode is unknown.
+absl::optional<int> ScalabilityModeStringToNumTemporalLayers(
+    absl::string_view scalability_mode_string);
+
+}  // namespace webrtc
+
+#endif  // API_VIDEO_CODECS_SCALABILITY_MODE_HELPER_H_