[PATCH v3 0/2] cec-follower: increase accuracy Audio Rate Control

[PATCH v3 0/2] cec-follower: increase accuracy Audio Rate Control

[Deborah Brouwer]

Changes since v2:
* Patch 1:
cec-follower: increase precision of Audio Rate Control active sensing
	* Add the unit (nanoseconds) as a suffix to the define name.
	* Write the defined value as a multiplication of seconds times
	  nsecs_per_sec.
	* Add ULL to help cast the expression to an unsigned long long.
	* Note: for the sake of clarity in the diff, a blank line before
	  the if statement is missing but it is subsequently added by Patch 2.

* Patch 2:
 cec-follower: detect the cessation of Audio Rate Control messages
	* Remove double negative in comment.
	* Extend comment to specify (i.e. state.last_aud_rate_rx_ts != 0).
	* Make warning message more succinct.

Changes since v1:
* Patch 1: cec-follower: increase precision of Audio Rate Control active sensing
	* new patch

*Patch 2:
	* Keep the aud_rate_msg_interval_check in processMsg to avoid missing
	  late messages that arrive between periodic interval checks.
	* Swap arguments so that struct node appears first.
	* Add blank line for readability.

Deborah Brouwer (2):
  cec-follower: increase precision of Audio Rate Control active sensing
  cec-follower: detect the cessation of Audio Rate Control messages

 utils/cec-follower/cec-processing.cpp | 30 ++++++++++++++++-----------
 1 file changed, 18 insertions(+), 12 deletions(-)

--
2.17.1

[PATCH v3 1/2] cec-follower: increase precision of Audio Rate Control active sensing

[Deborah Brouwer]

Measure the interval since the last audio rate control message in
nanoseconds instead of seconds. Increasing the precision catches audio
rate messages that are late by less than a second.

Signed-off-by: Deborah Brouwer <deborahbrouwer3563@gmail.com>
---
 utils/cec-follower/cec-processing.cpp | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/utils/cec-follower/cec-processing.cpp b/utils/cec-follower/cec-processing.cpp
index 93db4059..fcb55df2 100644
--- a/utils/cec-follower/cec-processing.cpp
+++ b/utils/cec-follower/cec-processing.cpp
@@ -29,8 +29,8 @@
 /* Time between each polling message sent to a device */
 #define POLL_PERIOD 15000
 
-/* The maximum interval in seconds between audio rate messages as defined in the spec */
-#define MAX_AUD_RATE_MSG_INTERVAL 2
+/* The maximum interval in nanoseconds between audio rate messages as defined in the spec */
+#define MAX_AUD_RATE_MSG_INTERVAL_NS (2 * 1000000000ULL)
 
 struct cec_enum_values {
 	const char *type_name;
@@ -241,8 +241,8 @@ static void aud_rate_msg_interval_check(__u64 ts_new, __u64 ts_old)
 	 * turned off the audio rate control.
 	 */
 	if (ts_old) {
-		unsigned interval = (ts_new - ts_old) / 1000000000;
-		if (interval > MAX_AUD_RATE_MSG_INTERVAL) {
+		__u64 interval = ts_new - ts_old;
+		if (interval > MAX_AUD_RATE_MSG_INTERVAL_NS) {
 			warn("The interval between Audio Rate Control messages was greater\n");
 			warn("than the Maxiumum Audio Rate Message Interval (2s).\n");
 		}
-- 
2.17.1

[PATCH v3 2/2] cec-follower: detect the cessation of Audio Rate Control messages

[Deborah Brouwer]

If the controlling device simply stops sending audio rate messages, give
the cec-follower the ability to detect that it has not received an audio
rate message within 2 seconds as required.  The cec-follower will quit the
audio rate controlled mode. Eliminate the need to measure an interval
between two audio rate messages.

Signed-off-by: Deborah Brouwer <deborahbrouwer3563@gmail.com>
---
 utils/cec-follower/cec-processing.cpp | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/utils/cec-follower/cec-processing.cpp b/utils/cec-follower/cec-processing.cpp
index fcb55df2..c76ec54e 100644
--- a/utils/cec-follower/cec-processing.cpp
+++ b/utils/cec-follower/cec-processing.cpp
@@ -233,18 +233,21 @@ static __u8 current_power_state(struct node *node)
 	return CEC_OP_POWER_STATUS_TO_STANDBY;
 }
 
-static void aud_rate_msg_interval_check(__u64 ts_new, __u64 ts_old)
+static void aud_rate_msg_interval_check(struct node *node, __u64 ts_new)
 {
 	/*
-	 * The interval between messages is not relevant if this is the
-	 * first audio rate control message or if the previous message
-	 * turned off the audio rate control.
+	 * The interval since the last audio rate message is only relevant
+	 * if the Source is currently in audio rate controlled mode
+	 * (i.e. state.last_aud_rate_rx_ts != 0).
 	 */
+	__u64 ts_old = node->state.last_aud_rate_rx_ts;
+
 	if (ts_old) {
 		__u64 interval = ts_new - ts_old;
+
 		if (interval > MAX_AUD_RATE_MSG_INTERVAL_NS) {
-			warn("The interval between Audio Rate Control messages was greater\n");
-			warn("than the Maxiumum Audio Rate Message Interval (2s).\n");
+			warn("The interval since the last Audio Rate Control message was > 2s.\n");
+			node->state.last_aud_rate_rx_ts = 0;
 		}
 	}
 }
@@ -802,7 +805,7 @@ static void processMsg(struct node *node, struct cec_msg &msg, unsigned me)
 
 		switch (msg.msg[2]) {
 		case CEC_OP_AUD_RATE_OFF:
-			aud_rate_msg_interval_check(msg.rx_ts, node->state.last_aud_rate_rx_ts);
+			aud_rate_msg_interval_check(node, msg.rx_ts);
 			node->state.last_aud_rate_rx_ts = 0;
 			return;
 		case CEC_OP_AUD_RATE_WIDE_STD:
@@ -811,7 +814,7 @@ static void processMsg(struct node *node, struct cec_msg &msg, unsigned me)
 		case CEC_OP_AUD_RATE_NARROW_STD:
 		case CEC_OP_AUD_RATE_NARROW_FAST:
 		case CEC_OP_AUD_RATE_NARROW_SLOW:
-			aud_rate_msg_interval_check(msg.rx_ts, node->state.last_aud_rate_rx_ts);
+			aud_rate_msg_interval_check(node, msg.rx_ts);
 			node->state.last_aud_rate_rx_ts = msg.rx_ts;
 			return;
 		default:
@@ -1033,6 +1036,9 @@ void testProcessing(struct node *node, bool wallclock)
 				node->state.rc_state = NOPRESS;
 			}
 		}
+
+		if (node->has_aud_rate)
+			aud_rate_msg_interval_check(node, ts_now);
 	}
 	mode = CEC_MODE_INITIATOR;
 	doioctl(node, CEC_S_MODE, &mode);
-- 
2.17.1