iOS HW H264 support.

First step towards supporting H264 on iOS. More tuning/experimentation
required in future CLs. Tested using AppRTCDemo on iPhone6 + iPad Mini.
Future work to get it working on OS/X, simulator (renders black screen
currently) and with the Android AppRTCDemo. Currently protected with a
compile time guard.

BUG=4081
R=andrew@webrtc.org, haysc@webrtc.org, holmer@google.com, jiayl@webrtc.org, kjellander@webrtc.org, pbos@webrtc.org, phoglund@webrtc.org, stefan@webrtc.org

Review URL: https://codereview.webrtc.org/1187573004.

Cr-Commit-Position: refs/heads/master@{#9515}
diff --git a/talk/examples/objc/AppRTCDemo/ARDAppClient.m b/talk/examples/objc/AppRTCDemo/ARDAppClient.m
index 0f3c423..ac99ca2 100644
--- a/talk/examples/objc/AppRTCDemo/ARDAppClient.m
+++ b/talk/examples/objc/AppRTCDemo/ARDAppClient.m
@@ -42,6 +42,7 @@
 #import "ARDCEODTURNClient.h"
 #import "ARDJoinResponse.h"
 #import "ARDMessageResponse.h"
+#import "ARDSDPUtils.h"
 #import "ARDSignalingMessage.h"
 #import "ARDUtilities.h"
 #import "ARDWebSocketChannel.h"
@@ -344,10 +345,15 @@
       [_delegate appClient:self didError:sdpError];
       return;
     }
+    // Prefer H264 if available.
+    RTCSessionDescription *sdpPreferringH264 =
+        [ARDSDPUtils descriptionForDescription:sdp
+                           preferredVideoCodec:@"H264"];
     [_peerConnection setLocalDescriptionWithDelegate:self
-                                  sessionDescription:sdp];
+                                  sessionDescription:sdpPreferringH264];
     ARDSessionDescriptionMessage *message =
-        [[ARDSessionDescriptionMessage alloc] initWithDescription:sdp];
+        [[ARDSessionDescriptionMessage alloc]
+            initWithDescription:sdpPreferringH264];
     [self sendSignalingMessage:message];
   });
 }
@@ -441,8 +447,12 @@
       ARDSessionDescriptionMessage *sdpMessage =
           (ARDSessionDescriptionMessage *)message;
       RTCSessionDescription *description = sdpMessage.sessionDescription;
+      // Prefer H264 if available.
+      RTCSessionDescription *sdpPreferringH264 =
+          [ARDSDPUtils descriptionForDescription:description
+                             preferredVideoCodec:@"H264"];
       [_peerConnection setRemoteDescriptionWithDelegate:self
-                                     sessionDescription:description];
+                                     sessionDescription:sdpPreferringH264];
       break;
     }
     case kARDSignalingMessageTypeCandidate: {
diff --git a/talk/examples/objc/AppRTCDemo/ARDSDPUtils.h b/talk/examples/objc/AppRTCDemo/ARDSDPUtils.h
new file mode 100644
index 0000000..2f14e6d
--- /dev/null
+++ b/talk/examples/objc/AppRTCDemo/ARDSDPUtils.h
@@ -0,0 +1,41 @@
+/*
+ * libjingle
+ * Copyright 2015 Google Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *  1. Redistributions of source code must retain the above copyright notice,
+ *     this list of conditions and the following disclaimer.
+ *  2. Redistributions in binary form must reproduce the above copyright notice,
+ *     this list of conditions and the following disclaimer in the documentation
+ *     and/or other materials provided with the distribution.
+ *  3. The name of the author may not be used to endorse or promote products
+ *     derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
+ * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+ * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#import <Foundation/Foundation.h>
+
+@class RTCSessionDescription;
+
+@interface ARDSDPUtils : NSObject
+
+// Updates the original SDP description to instead prefer the specified video
+// codec. We do this by placing the specified codec at the beginning of the
+// codec list if it exists in the sdp.
++ (RTCSessionDescription *)
+    descriptionForDescription:(RTCSessionDescription *)description
+          preferredVideoCodec:(NSString *)codec;
+
+@end
diff --git a/talk/examples/objc/AppRTCDemo/ARDSDPUtils.m b/talk/examples/objc/AppRTCDemo/ARDSDPUtils.m
new file mode 100644
index 0000000..157d6fc
--- /dev/null
+++ b/talk/examples/objc/AppRTCDemo/ARDSDPUtils.m
@@ -0,0 +1,108 @@
+/*
+ * libjingle
+ * Copyright 2015 Google Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *  1. Redistributions of source code must retain the above copyright notice,
+ *     this list of conditions and the following disclaimer.
+ *  2. Redistributions in binary form must reproduce the above copyright notice,
+ *     this list of conditions and the following disclaimer in the documentation
+ *     and/or other materials provided with the distribution.
+ *  3. The name of the author may not be used to endorse or promote products
+ *     derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
+ * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+ * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#import "ARDSDPUtils.h"
+
+#import "RTCSessionDescription.h"
+
+@implementation ARDSDPUtils
+
++ (RTCSessionDescription *)
+    descriptionForDescription:(RTCSessionDescription *)description
+          preferredVideoCodec:(NSString *)codec {
+  NSString *sdpString = description.description;
+  NSString *lineSeparator = @"\n";
+  NSString *mLineSeparator = @" ";
+  // Copied from PeerConnectionClient.java.
+  // TODO(tkchin): Move this to a shared C++ file.
+  NSMutableArray *lines =
+      [NSMutableArray arrayWithArray:
+          [sdpString componentsSeparatedByString:lineSeparator]];
+  int mLineIndex = -1;
+  NSString *codecRtpMap = nil;
+  // a=rtpmap:<payload type> <encoding name>/<clock rate>
+  // [/<encoding parameters>]
+  NSString *pattern =
+      [NSString stringWithFormat:@"^a=rtpmap:(\\d+) %@(/\\d+)+[\r]?$", codec];
+  NSRegularExpression *regex =
+      [NSRegularExpression regularExpressionWithPattern:pattern
+                                                options:0
+                                                  error:nil];
+  for (NSInteger i = 0; (i < lines.count) && (mLineIndex == -1 || !codecRtpMap);
+       ++i) {
+    NSString *line = lines[i];
+    if ([line hasPrefix:@"m=video"]) {
+      mLineIndex = i;
+      continue;
+    }
+    NSTextCheckingResult *codecMatches =
+        [regex firstMatchInString:line
+                          options:0
+                            range:NSMakeRange(0, line.length)];
+    if (codecMatches) {
+      codecRtpMap =
+          [line substringWithRange:[codecMatches rangeAtIndex:1]];
+      continue;
+    }
+  }
+  if (mLineIndex == -1) {
+    NSLog(@"No m=video line, so can't prefer %@", codec);
+    return description;
+  }
+  if (!codecRtpMap) {
+    NSLog(@"No rtpmap for %@", codec);
+    return description;
+  }
+  NSArray *origMLineParts =
+      [lines[mLineIndex] componentsSeparatedByString:mLineSeparator];
+  if (origMLineParts.count > 3) {
+    NSMutableArray *newMLineParts =
+        [NSMutableArray arrayWithCapacity:origMLineParts.count];
+    NSInteger origPartIndex = 0;
+    // Format is: m=<media> <port> <proto> <fmt> ...
+    [newMLineParts addObject:origMLineParts[origPartIndex++]];
+    [newMLineParts addObject:origMLineParts[origPartIndex++]];
+    [newMLineParts addObject:origMLineParts[origPartIndex++]];
+    [newMLineParts addObject:codecRtpMap];
+    for (; origPartIndex < origMLineParts.count; ++origPartIndex) {
+      if (![codecRtpMap isEqualToString:origMLineParts[origPartIndex]]) {
+        [newMLineParts addObject:origMLineParts[origPartIndex]];
+      }
+    }
+    NSString *newMLine =
+        [newMLineParts componentsJoinedByString:mLineSeparator];
+    [lines replaceObjectAtIndex:mLineIndex
+                     withObject:newMLine];
+  } else {
+    NSLog(@"Wrong SDP media description format: %@", lines[mLineIndex]);
+  }
+  NSString *mangledSdpString = [lines componentsJoinedByString:lineSeparator];
+  return [[RTCSessionDescription alloc] initWithType:description.type
+                                                 sdp:mangledSdpString];
+}
+
+@end
diff --git a/talk/examples/objc/AppRTCDemo/tests/ARDAppClientTest.mm b/talk/examples/objc/AppRTCDemo/tests/ARDAppClientTest.mm
index 396f64f..47df526 100644
--- a/talk/examples/objc/AppRTCDemo/tests/ARDAppClientTest.mm
+++ b/talk/examples/objc/AppRTCDemo/tests/ARDAppClientTest.mm
@@ -31,8 +31,10 @@
 #import "ARDAppClient+Internal.h"
 #import "ARDJoinResponse+Internal.h"
 #import "ARDMessageResponse+Internal.h"
+#import "ARDSDPUtils.h"
 #import "RTCMediaConstraints.h"
 #import "RTCPeerConnectionFactory.h"
+#import "RTCSessionDescription.h"
 
 #include "webrtc/base/gunit.h"
 #include "webrtc/base/ssladapter.h"
@@ -304,6 +306,27 @@
 
 @end
 
+@interface ARDSDPUtilsTest : ARDTestCase
+- (void)testPreferVideoCodec;
+@end
+
+@implementation ARDSDPUtilsTest
+
+- (void)testPreferVideoCodec {
+  NSString *sdp = @("m=video 9 RTP/SAVPF 100 116 117 96 120\n"
+                    "a=rtpmap:120 H264/90000\n");
+  NSString *expectedSdp = @("m=video 9 RTP/SAVPF 120 100 116 117 96\n"
+                            "a=rtpmap:120 H264/90000\n");
+  RTCSessionDescription* desc =
+      [[RTCSessionDescription alloc] initWithType:@"offer" sdp:sdp];
+  RTCSessionDescription *h264Desc =
+      [ARDSDPUtils descriptionForDescription:desc
+                         preferredVideoCodec:@"H264"];
+  EXPECT_TRUE([h264Desc.description isEqualToString:expectedSdp]);
+}
+
+@end
+
 class SignalingTest : public ::testing::Test {
  protected:
   static void SetUpTestCase() {
@@ -320,3 +343,12 @@
     [test testSession];
   }
 }
+
+TEST_F(SignalingTest, SDPTest) {
+  @autoreleasepool {
+    ARDSDPUtilsTest *test = [[ARDSDPUtilsTest alloc] init];
+    [test testPreferVideoCodec];
+  }
+}
+
+