cast: Support for low-latency interactive mode

chrome/renderer/extensions/cast_streaming_native_handler.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/renderer/extensions/cast_streaming_native_handler.h"
 
 #include <functional>
 #include <iterator>
 
 #include "base/location.h"
@@ skipping 71 matching lines @@
 }
 }  // namespace
 
 bool ToCastRtpPayloadParamsOrThrow(v8::Isolate* isolate,
                                    const RtpPayloadParams& ext_params,
                                    CastRtpPayloadParams* cast_params) {
   cast_params->payload_type = ext_params.payload_type;
   cast_params->max_latency_ms = ext_params.max_latency;
   cast_params->min_latency_ms =
       ext_params.min_latency ? *ext_params.min_latency : ext_params.max_latency;
+  cast_params->animated_latency_ms = ext_params.animated_latency
+                                         ? *ext_params.animated_latency
+                                         : ext_params.max_latency;

[miu, 2015/12/03 21:26:22]

I think the "else" clause of this expression will return nullptr casted to a
zero integer.  Instead, should we just use a default, bounded within min and
max?  Something like:

  if (cast_params->min_latency_ms > cast_params->max_latency_ms)
    return false;

  ...

  if (cast_params->min_latency_ms <= 0) {
    cast_params->animated_latency_ms = max_latency_ms;
  } else {
    cast_params->animated_latency_ms =
        std::min(cast_params->max_latency_ms,
std::max(cast_params->min_latency_ms, kDefaultAnimatedLatencyMillis));
  }

[Irfan, 2015/12/04 22:45:36]

The else part of the expression is returning an int. max_latency is a mandatory
parameter (and hence an int). If there are no animation/min params passed, they
default to the max value.

[miu, 2015/12/08 00:16:16]

Acknowledged.

   cast_params->codec_name = ext_params.codec_name;
   cast_params->ssrc = ext_params.ssrc;
   cast_params->feedback_ssrc = ext_params.feedback_ssrc;
   cast_params->clock_rate = ext_params.clock_rate ? *ext_params.clock_rate : 0;
   cast_params->min_bitrate =
       ext_params.min_bitrate ? *ext_params.min_bitrate : 0;
   cast_params->max_bitrate =
       ext_params.max_bitrate ? *ext_params.max_bitrate : 0;
   cast_params->channels = ext_params.channels ? *ext_params.channels : 0;
   cast_params->max_frame_rate =
@@ skipping 17 matching lines @@
     cast_params->codec_specific_params.push_back(cast_codec_params);
   }
   return true;
 }
 
 void FromCastRtpPayloadParams(const CastRtpPayloadParams& cast_params,
                               RtpPayloadParams* ext_params) {
   ext_params->payload_type = cast_params.payload_type;
   ext_params->max_latency = cast_params.max_latency_ms;
   ext_params->min_latency.reset(new int(cast_params.min_latency_ms));
+  ext_params->animated_latency.reset(new int(cast_params.animated_latency_ms));
   ext_params->codec_name = cast_params.codec_name;
   ext_params->ssrc = cast_params.ssrc;
   ext_params->feedback_ssrc = cast_params.feedback_ssrc;
   if (cast_params.clock_rate)
     ext_params->clock_rate.reset(new int(cast_params.clock_rate));
   if (cast_params.min_bitrate)
     ext_params->min_bitrate.reset(new int(cast_params.min_bitrate));
   if (cast_params.max_bitrate)
     ext_params->max_bitrate.reset(new int(cast_params.max_bitrate));
   if (cast_params.channels)
@@ skipping 711 matching lines @@
 void CastStreamingNativeHandler::AddTracksToMediaStream(
     const std::string& url,
     const media::AudioParameters& params,
     scoped_refptr<media::AudioCapturerSource> audio,
     scoped_ptr<media::VideoCapturerSource> video) {
   content::AddAudioTrackToMediaStream(audio, params, true, true, url);
   content::AddVideoTrackToMediaStream(video.Pass(), true, true, url);
 }
 
 }  // namespace extensions