1 files changed, 121 insertions, 0 deletions
diff --git a/third_party/libwebrtc/media/base/sdp_video_format_utils.cc b/third_party/libwebrtc/media/base/sdp_video_format_utils.cc
new file mode 100644
index 0000000000..a156afdc02
--- /dev/null
+++ b/third_party/libwebrtc/media/base/sdp_video_format_utils.cc
@@ -0,0 +1,121 @@
+/*
+ *  Copyright (c) 2019 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 "media/base/sdp_video_format_utils.h"
+
+#include <cstring>
+#include <map>
+#include <utility>
+
+#include "api/video_codecs/h264_profile_level_id.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/string_to_number.h"
+
+namespace webrtc {
+namespace {
+const char kProfileLevelId[] = "profile-level-id";
+const char kH264LevelAsymmetryAllowed[] = "level-asymmetry-allowed";
+// Max frame rate for VP8 and VP9 video.
+const char kVPxFmtpMaxFrameRate[] = "max-fr";
+// Max frame size for VP8 and VP9 video.
+const char kVPxFmtpMaxFrameSize[] = "max-fs";
+const int kVPxFmtpFrameSizeSubBlockPixels = 256;
+
+bool IsH264LevelAsymmetryAllowed(const SdpVideoFormat::Parameters& params) {
+  const auto it = params.find(kH264LevelAsymmetryAllowed);
+  return it != params.end() && strcmp(it->second.c_str(), "1") == 0;
+}
+
+// Compare H264 levels and handle the level 1b case.
+bool H264LevelIsLess(H264Level a, H264Level b) {
+  if (a == H264Level::kLevel1_b)
+    return b != H264Level::kLevel1 && b != H264Level::kLevel1_b;
+  if (b == H264Level::kLevel1_b)
+    return a == H264Level::kLevel1;
+  return a < b;
+}
+
+H264Level H264LevelMin(H264Level a, H264Level b) {
+  return H264LevelIsLess(a, b) ? a : b;
+}
+
+absl::optional<int> ParsePositiveNumberFromParams(
+    const SdpVideoFormat::Parameters& params,
+    const char* parameter_name) {
+  const auto max_frame_rate_it = params.find(parameter_name);
+  if (max_frame_rate_it == params.end())
+    return absl::nullopt;
+
+  const absl::optional<int> i =
+      rtc::StringToNumber<int>(max_frame_rate_it->second);
+  if (!i.has_value() || i.value() <= 0)
+    return absl::nullopt;
+  return i;
+}
+
+}  // namespace
+
+// Set level according to https://tools.ietf.org/html/rfc6184#section-8.2.2.
+void H264GenerateProfileLevelIdForAnswer(
+    const SdpVideoFormat::Parameters& local_supported_params,
+    const SdpVideoFormat::Parameters& remote_offered_params,
+    SdpVideoFormat::Parameters* answer_params) {
+  // If both local and remote haven't set profile-level-id, they are both using
+  // the default profile. In this case, don't set profile-level-id in answer
+  // either.
+  if (!local_supported_params.count(kProfileLevelId) &&
+      !remote_offered_params.count(kProfileLevelId)) {
+    return;
+  }
+
+  // Parse profile-level-ids.
+  const absl::optional<H264ProfileLevelId> local_profile_level_id =
+      ParseSdpForH264ProfileLevelId(local_supported_params);
+  const absl::optional<H264ProfileLevelId> remote_profile_level_id =
+      ParseSdpForH264ProfileLevelId(remote_offered_params);
+  // The local and remote codec must have valid and equal H264 Profiles.
+  RTC_DCHECK(local_profile_level_id);
+  RTC_DCHECK(remote_profile_level_id);
+  RTC_DCHECK_EQ(local_profile_level_id->profile,
+                remote_profile_level_id->profile);
+
+  // Parse level information.
+  const bool level_asymmetry_allowed =
+      IsH264LevelAsymmetryAllowed(local_supported_params) &&
+      IsH264LevelAsymmetryAllowed(remote_offered_params);
+  const H264Level local_level = local_profile_level_id->level;
+  const H264Level remote_level = remote_profile_level_id->level;
+  const H264Level min_level = H264LevelMin(local_level, remote_level);
+
+  // Determine answer level. When level asymmetry is not allowed, level upgrade
+  // is not allowed, i.e., the level in the answer must be equal to or lower
+  // than the level in the offer.
+  const H264Level answer_level =
+      level_asymmetry_allowed ? local_level : min_level;
+
+  // Set the resulting profile-level-id in the answer parameters.
+  (*answer_params)[kProfileLevelId] = *H264ProfileLevelIdToString(
+      H264ProfileLevelId(local_profile_level_id->profile, answer_level));
+}
+
+absl::optional<int> ParseSdpForVPxMaxFrameRate(
+    const SdpVideoFormat::Parameters& params) {
+  return ParsePositiveNumberFromParams(params, kVPxFmtpMaxFrameRate);
+}
+
+absl::optional<int> ParseSdpForVPxMaxFrameSize(
+    const SdpVideoFormat::Parameters& params) {
+  const absl::optional<int> i =
+      ParsePositiveNumberFromParams(params, kVPxFmtpMaxFrameSize);
+  return i ? absl::make_optional(i.value() * kVPxFmtpFrameSizeSubBlockPixels)
+           : absl::nullopt;
+}
+
+}  // namespace webrtc