cast: Support for low-latency interactive mode

media/cast/sender/frame_sender.h

Index: media/cast/sender/frame_sender.h
diff --git a/media/cast/sender/frame_sender.h b/media/cast/sender/frame_sender.h
index d3b925e6dcf0e8d74a1dfb7e51cd1343e7a11f6e..58ba0a721d0b0eb35368bf45f08b4e3981529afa 100644
--- a/media/cast/sender/frame_sender.h
+++ b/media/cast/sender/frame_sender.h
@@ -20,6 +20,15 @@
 namespace media {
 namespace cast {
 
+// Starting playout time when we enter interactive mode.
+const int kInteractiveModeStartPlayoutTimeMs = 120;

[miu, 2015/12/01 21:15:27]

Rather than as constants, these should be plumbed-in as Audio/VideoSenderConfig,
and all the way up through to the extension API.  See media/cast/cast_config.h,
chrome/common/extensions/api/cast_streaming_rtp_stream.idl, and
chrome/renderer/media/cast_rtp_stream.cc.  This will allow us to run experiments
to determine ideal values, and also to turn on/off this new feature with Cast
Extension releases.

[Irfan, 2015/12/02 22:32:44]

I thought about this and have gone with following:

- We can levarage min as the starting point for interactive mode (since a value
less than that does not make much sense)

- Added a new animated playout delay value that is in between min and max so we
can adjust for movie playback dynamically

+
+// Starting playout time when we encounter a need to drop a frame while in
+// non-interactive mode. This is chosen to be a value that is known to work
+// well for animation content in order to minimize freezing while switching
+// between interactive and non-interactive mode.
+const int kNonInteractiveModeStartPlayoutTimeMs = 400;
+
 struct SenderEncodedFrame;
 
 class FrameSender {