Add to-string function for H264 profile level id

webrtc/common_video/h264/profile_level_id.cc

 /*
  *  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.
  */
 
 #include "webrtc/common_video/h264/profile_level_id.h"
 
+#include <cstdio>
 #include <cstdlib>
 #include <cstring>
 
 namespace {
 
 // For level_idc=11 and profile_idc=0x42, 0x4D, or 0x58, the constraint set3
 // flag specifies if level 1b or level 1.1 is used.
 const uint8_t kConstraintSet3Flag = 0x10;
 
 // Convert a string of 8 characters into a byte where the positions containing
@@ skipping 98 matching lines @@
     if (profile_idc == pattern.profile_idc &&
         pattern.profile_iop.IsMatch(profile_iop)) {
       return rtc::Optional<ProfileLevelId>({pattern.profile, level});
     }
   }
 
   // Unrecognized profile_idc/profile_iop combination.
   return rtc::Optional<ProfileLevelId>();
 }
 
+std::string ProfileLevelIdToString(const ProfileLevelId& profile_level_id) {
+  // Handle special case level == 1b.
+  if (profile_level_id.level == kLevel1_b) {
+    switch (profile_level_id.profile) {
+      case kProfileConstrainedBaseline:
+        return "42f00b";
+      case kProfileBaseline:
+        return "42100b";
+      case kProfileMain:
+        return "4D100b";
+      // Level 1b is not allowed for other profiles.
+      default:
+        return std::string();

[kthelgason, 2016/11/03 09:39:05]

Maybe we should return an rtc::Optional<std::string> here, so the callee doesn't
have to remember to check for an empty string.

[magjed_webrtc, 2016/11/03 12:31:16]

You are probably right. It's clearer than returning an empty string and the type
system will enforce checking against it.

+    }
+  }
+
+  const char* profile_idc_iop_string;
+  switch (profile_level_id.profile) {
+    case kProfileConstrainedBaseline:
+      profile_idc_iop_string = "42e0";
+      break;
+    case kProfileBaseline:
+      profile_idc_iop_string = "4200";
+      break;
+    case kProfileMain:
+      profile_idc_iop_string = "4D00";
+      break;
+    case kProfileConstrainedHigh:
+      profile_idc_iop_string = "640c";
+      break;
+    case kProfileHigh:
+      profile_idc_iop_string = "6400";
+      break;
+    // Unrecognized profile.
+    default:
+      return std::string();

[kthelgason, 2016/11/03 09:39:05]

perhaps replace this with a RTC_NOTREACHED() if we expect this to never happen.

[magjed_webrtc, 2016/11/03 12:31:16]

If we handle some case, then we should not CHECK/NOT_REACHED also. This is from
the style guide:
"... A consequence of this is that you should not handle DCHECK() failures, even
if failure would result in a crash. Attempting to handle a DCHECK() failure is a
statement that the DCHECK() can fail, which contradicts the point of writing the
DCHECK()."

+  }
+
+  char str[7];
+  snprintf(str, 7u, "%s%02x", profile_idc_iop_string, profile_level_id.level);
+  return str;
+}
+
 }  // namespace H264
 }  // namespace webrtc