Add function for getting supported H264 level from max resolution and fps

webrtc/common_video/h264/profile_level_id.h

 /*
  *  Copyright (c) 2016 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.
  */
 
@@ skipping 42 matching lines @@
       : profile(profile), level(level) {}
   Profile profile;
   Level level;
 };
 
 // Parse profile level id that is represented as a string of 3 hex bytes.
 // Nothing will be returned if the string is not a recognized H264
 // profile level id.
 rtc::Optional<ProfileLevelId> ParseProfileLevelId(const char* str);
 
+// Given that a decoder supports up to a given frame size (in pixels) at up to a
+// given number of frames per second, return the highest H.264 level where it
+// can guarantee that it will be able to support all valid encoded streams that
+// are within that level.
+rtc::Optional<Level> SupportedLevel(int max_frame_pixel_count, int max_fps);

[hta-webrtc, 2016/11/08 09:21:16]

Suggest using a float or double for max_fps. The conversion between the two
forms is hurtful in the codebase, and whenever we get content at 29.94 FPS, odd
stuff happens.

[magjed_webrtc, 2016/11/08 10:29:23]

Done, changed to float.

+
 // Returns canonical string representation as three hex bytes of the profile
 // level id, or returns nothing for invalid profile level ids.
 rtc::Optional<std::string> ProfileLevelIdToString(
     const ProfileLevelId& profile_level_id);
 
 }  // namespace H264
 }  // namespace webrtc
 
 #endif  // WEBRTC_COMMON_VIDEO_H264_PROFILE_LEVEL_ID_H_