iOS HW H264 support.

talk/examples/objc/AppRTCDemo/ARDSDPUtils.m

+/*
+ * 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
+

[phoglund, 2015/06/22 08:17:38]

This looks like something that would greatly benefit from a unit test. You
should be able to straightforwardly feed in session descriptions and test that
the SDP that comes out at the other end is correct?

++ (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