Simple Default ObjC video codec factories.

Move the simple video encoder/decoder factory from AppRTCMobile into the
public API so users who don't have special requirements for video codecs
can easily get started.

Also clean up the API a little.

This CL replaces the more flexible default factories in
https://webrtc-review.googlesource.com/c/src/+/7741 and clients that
want to implement their own codecs will have to supply their own
encoder/decoder factories as well. The benefits of the approach in
this CL are a simpler API and less effects on the rest of the code.

Bug: None
Change-Id: I4ed94090d778b4fc38b49864de1d4de4ff125d6a
Reviewed-on: https://webrtc-review.googlesource.com/15141
Reviewed-by: Kári Helgason <kthelgason@webrtc.org>
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Commit-Queue: Anders Carlsson <andersc@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20441}

sdk/objc/Framework/Classes/PeerConnection/RTCDefaultVideoEncoderFactory.m

@@ -0,0 +1,74 @@
+/*
+ *  Copyright 2017 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.
+ */
+
+#import "WebRTC/RTCVideoCodecFactory.h"
+
+#import "WebRTC/RTCVideoCodec.h"
+#import "WebRTC/RTCVideoCodecH264.h"
+#import "WebRTC/RTCVideoEncoderVP8.h"
+#import "WebRTC/RTCVideoEncoderVP9.h"
+
+@implementation RTCDefaultVideoEncoderFactory
+
+@synthesize preferredCodec;
+
++ (NSArray<RTCVideoCodecInfo *> *)supportedCodecs {
+  NSDictionary<NSString *, NSString *> *constrainedHighParams = @{
+    @"profile-level-id" : kRTCLevel31ConstrainedHigh,
+    @"level-asymmetry-allowed" : @"1",
+    @"packetization-mode" : @"1",
+  };
+  RTCVideoCodecInfo *constrainedHighInfo =
+      [[RTCVideoCodecInfo alloc] initWithName:kRTCVideoCodecH264Name
+                                   parameters:constrainedHighParams];
+
+  NSDictionary<NSString *, NSString *> *constrainedBaselineParams = @{
+    @"profile-level-id" : kRTCLevel31ConstrainedBaseline,
+    @"level-asymmetry-allowed" : @"1",
+    @"packetization-mode" : @"1",
+  };
+  RTCVideoCodecInfo *constrainedBaselineInfo =
+      [[RTCVideoCodecInfo alloc] initWithName:kRTCVideoCodecH264Name
+                                   parameters:constrainedBaselineParams];
+
+  RTCVideoCodecInfo *vp8Info = [[RTCVideoCodecInfo alloc] initWithName:kRTCVideoCodecVp8Name];
+
+  RTCVideoCodecInfo *vp9Info = [[RTCVideoCodecInfo alloc] initWithName:kRTCVideoCodecVp9Name];
+
+  return @[ constrainedHighInfo, constrainedBaselineInfo, vp8Info, vp9Info ];
+}
+
+- (id<RTCVideoEncoder>)createEncoder:(RTCVideoCodecInfo *)info {
+  if ([info.name isEqualToString:kRTCVideoCodecH264Name]) {
+    return [[RTCVideoEncoderH264 alloc] initWithCodecInfo:info];
+  } else if ([info.name isEqualToString:kRTCVideoCodecVp8Name]) {
+    return [RTCVideoEncoderVP8 vp8Encoder];
+  } else if ([info.name isEqualToString:kRTCVideoCodecVp9Name]) {
+    return [RTCVideoEncoderVP9 vp9Encoder];
+  }
+
+  return nil;
+}
+
+- (NSArray<RTCVideoCodecInfo *> *)supportedCodecs {
+  NSMutableArray<RTCVideoCodecInfo *> *codecs = [[[self class] supportedCodecs] mutableCopy];
+
+  NSMutableArray<RTCVideoCodecInfo *> *orderedCodecs = [NSMutableArray array];
+  NSUInteger index = [codecs indexOfObject:self.preferredCodec];
+  if (index != NSNotFound) {
+    [orderedCodecs addObject:[codecs objectAtIndex:index]];
+    [codecs removeObjectAtIndex:index];
+  }
+  [orderedCodecs addObjectsFromArray:codecs];
+
+  return [orderedCodecs copy];
+}
+
+@end