Creating controller manager from config string in audio network adaptor.

webrtc/modules/audio_coding/audio_network_adaptor/config.proto

Index: webrtc/modules/audio_coding/audio_network_adaptor/config.proto
diff --git a/webrtc/modules/audio_coding/audio_network_adaptor/config.proto b/webrtc/modules/audio_coding/audio_network_adaptor/config.proto
new file mode 100644
index 0000000000000000000000000000000000000000..3c678fc1b64a48f453c8c6c063436a65dbdb69e0
--- /dev/null
+++ b/webrtc/modules/audio_coding/audio_network_adaptor/config.proto
@@ -0,0 +1,108 @@
+syntax = "proto2";
+option optimize_for = LITE_RUNTIME;
+package webrtc.audio_network_adaptor.config;
+
+message FecController {
+  message Threshold {
+    // Threshold defines a curve in the bandwidth/packet-loss domain. The
+    // curve is characterized by the two conjunction points: A and B.
+    //
+    // packet ^  |
+    //  loss  | A|
+    //        |   \        A: (low_bandwidth_bps, low_bandwidth_packet_loss)
+    //        |    \       B: (high_bandwidth_bps, high_bandwidth_packet_loss)
+    //        |    B\________
+    //        |---------------> bandwidth
+    optional int32 low_bandwidth_bps = 1;
+    optional float low_bandwidth_packet_loss = 2;
+    optional int32 high_bandwidth_bps = 3;
+    optional float high_bandwidth_packet_loss = 4;
+  }
+
+  // |fec_enabling_threshold| defines a curve, above which FEC should be
+  // enabled. |fec_disabling_threshold| defines a curve, under which FEC
+  // should be disabled. See below
+  //
+  // packet-loss ^   |  |
+  //             |   |  |   FEC
+  //             |    \  \   ON
+  //             | FEC \  \_______ fec_enabling_threshold
+  //             | OFF  \_________ fec_disabling_threshold
+  //             |-----------------> bandwidth
+  optional Threshold fec_enabling_threshold = 1;
+  optional Threshold fec_disabling_threshold = 2;
+
+  // |time_constant_ms| is the time constant for an exponential filter, which
+  // is used for smoothing the packet loss fraction.
+  optional int32 time_constant_ms = 3;
+}
+
+message FrameLengthController {
+  // Uplink packet loss fraction below which frame length can increase.
+  optional float fl_increasing_packet_loss_fraction = 1;

[terelius, 2016/09/29 13:01:13]

nit: I read this name as meaning that the packet loss is increasing, but the
comment suggests that it's the frame length that may/should increase. On the
other hand, I can't think of a better name. Change if you can think of a better
name, otherwise leave as is.

[minyue-webrtc, 2016/09/29 15:05:40]

We have been struggling for naming. We ended up using A_D-ing_B, which stands
for "B that D-s A", which is similar to "water boiling point". If you have
better ideas, we would be happy to change.

+
+  // Uplink packet loss fraction below which frame length should decrease.
+  optional float fl_decreasing_packet_loss_fraction = 2;
+
+  // Uplink bandwidth below which frame length can switch from 20ms to 60ms.
+  optional int32 fl_20ms_to_60ms_bandwidth_bps = 3;
+
+  // Uplink bandwidth above which frame length should switch from 60ms to 20ms.
+  optional int32 fl_60ms_to_20ms_bandwidth_bps = 4;
+}
+
+message ChannelController {
+  // Uplink bandwidth above which the number of encoded channels should switch
+  // from 1 to 2.
+  optional int32 channel_1_to_2_bandwidth_bps = 1;
+
+  // Uplink bandwidth below which the number of encoded channels should switch
+  // from 2 to 1.
+  optional int32 channel_2_to_1_bandwidth_bps = 2;
+}
+
+message DtxController {
+  // Uplink bandwidth below which DTX should be switched on.
+  optional int32 dtx_enabling_bandwidth_bps = 1;
+
+  // Uplink bandwidth above which DTX should be switched off.
+  optional int32 dtx_disabling_bandwidth_bps = 2;
+}
+
+message BitrateController {}
+
+message Controller {
+  message ScoringPoint {
+    // |ScoringPoint| is a subspace of network condition. It is used for
+    // comparing the significance of controllers.
+    optional int32 uplink_bandwidth_bps = 1;
+    optional float uplink_packet_loss_fraction = 2;
+  }
+
+  // The distance from |scoring_point| to a given network condition defines
+  // the significance of this controller with respect that network condition.

[terelius, 2016/09/29 13:01:13]

I don't quite understand the goal, but can a controller really be reduced to
"perfect decisions at a single point"? Maybe one controller is reliable at all
bitrates assuming no packet loss?

[minyue-webrtc, 2016/09/29 15:05:40]

That is a good point. If a controller wants to show a higher significance to
another controller at (any rates, 0 packet loss), the comparison of the two
controllers should be carried out with a different definition of ScoringPoint.
So ideally, each comparison of controllers should use its own criterion.
Fortunately, this definition is enough for current implementation.

If we need to introduce other definition of ScoringPoint, the proto can be
modified into

message Controller {
  message ScoringPoint;
  message ScoringPoint_2;
  oneof controller {
    ...
  }
  repeated Compare {
    optional Controller compare_with;
    oneof scoring_points {
      ScoringPoint      s1;
      ScoringPoint_2    s2;
    }
  }
}

But this change should only be made when we actually find its need.

+  // Shorter distance means higher significance. The significances of
+  // controllers determine their order in the processing pipeline. Controllers
+  // without |scoring_point| follow their default order in
+  // |ControllerManager::controllers|.
+  optional ScoringPoint scoring_point = 1;
+
+  oneof controller {

[terelius, 2016/09/29 13:01:13]

Can we use oneof? IIRC there was some reason why we couldn't use it in the event
log. (If there are no problems with it, we should start using it in the event
log.)

[minyue-webrtc, 2016/09/29 15:05:40]

I found cases in Chromium before I went for this. See
https://cs.chromium.org/chromium/src/blimp/common/proto/blimp_message.proto?q...
and
https://cs.chromium.org/chromium/src/media/remoting/proto/remoting_rpc_messag...

and it is relatively new. Follow the tracker:
https://bugs.chromium.org/p/chromium/issues/detail?id=570371
and
https://chromium.googlesource.com/chromium/src/+/1fc58a4b0bd5d0a58ce8a353a0c7...

+    FecController fec_controller = 21;
+    FrameLengthController frame_length_controller = 22;
+    ChannelController channel_controller = 23;
+    DtxController dtx_controller = 24;
+    BitrateController bitrate_controller = 25;
+  }
+}
+
+message ControllerManager {
+  repeated Controller controllers = 1;
+
+  // Least time since last reordering for a new reordering to be made.
+  optional int32 min_reordering_time_ms = 2;
+
+  // Least squared distance from last scoring point for a new reordering to be
+  // made.
+  optional float min_reordering_squared_distance = 3;
+}