Adding codecs to the RtpParameters returned by an RtpSender.

webrtc/api/objc/RTCRtpCodecParameters.h

 /*
  *  Copyright 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.
  */
 
 #import <Foundation/Foundation.h>
 
 NS_ASSUME_NONNULL_BEGIN
 
-@interface RTCRtpEncodingParameters : NSObject
+@interface RTCRtpCodecParameters : NSObject
 
-/** Controls whether the encoding is currently transmitted. */
-@property(nonatomic, assign) BOOL isActive;
+/** The RTP payload type. */
+@property(nonatomic, assign) int payloadType;

[tkchin_webrtc, 2016/04/14 17:52:51]

ditto enum?

[Taylor Brandstetter, 2016/04/14 18:17:22]

An enum for every value from 0 to 127?

[pthatcher1, 2016/04/14 18:27:15]

And since the values are dynamically assigned, at best the enum would be

PAYLOAD_TYPE_1
PAYLOAD_TYPE_2
PAYLOAD_TYPE_3

With the exception of perhaps PCMU and a few other random PTs that have static
values.

[tkchin_webrtc, 2016/04/14 18:30:08]

Interesting. How would a client assign this payload type then? 

[Taylor Brandstetter, 2016/04/14 20:01:47]

If a client wanted to add a new codec without SDP renegotiation (the ORTC way of
doing things) they might construct a codec from scratch and choose an available
payload type from the dynamic range.

[tkchin_webrtc, 2016/04/14 21:11:47]

Can we add a pointer to documentation for that, or just make this readonly?
I just wanted to avoid having a setter where it's not clear what the value
should be set to.

[Taylor Brandstetter, 2016/04/14 22:03:30]

Done.

 
-/** The maximum bitrate to use for the encoding, or nil if there is no
- *  limit.
+/**
+ * The codec MIME type. Valid types are listed in:
+ * http://www.iana.org/assignments/rtp-parameters/rtp-parameters.xhtml#rtp-parameters-2
  */
-@property(nonatomic, copy, nullable) NSNumber *maxBitrateBps;
+@property(nonatomic, nonnull) NSString *mimeType;

[tkchin_webrtc, 2016/04/14 17:52:51]

Use an enum for this and translate to what the C++ needs?

[Taylor Brandstetter, 2016/04/14 18:17:22]

There are a pretty lot of possibilities (100+) and more could be added. Granted,
we only support a small subset of them, but it still seems like overkill when an
application could use a string compare if it really needs to.

Also, this is a string in the JS API and I think it makes sense to keep the APIs
as similar as possible.

[tkchin_webrtc, 2016/04/14 18:30:08]

Ok. In that case please add supported strings as constants in this file?

[Taylor Brandstetter, 2016/04/14 20:01:47]

Ok. I copied them from mediaconstants.h/cc

+
+/** The codec clock rate expressed in Hertz. */
+@property(nonatomic, assign) int clockRate;
+
+/** The number of channels (mono=1, stereo=2). */
+@property(nonatomic, assign) int channels;
 
 - (instancetype)init NS_DESIGNATED_INITIALIZER;
 
 @end
 
 NS_ASSUME_NONNULL_END