Re: [Bluez-devel] yes, a2dp timing is whacked

[Brad Midgley <bmidgley@xmission.com>]

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Guys,

I put a rough proof-of-concept implementation together using setitimer. 
(Yes, it's gross and the signal handler doesn't actually do any work, 
just indicates that the interval is over)

The music seems to be timed right but it's a very "noisy" signal on the 
hp headset. Any ideas?

I didn't commit it because it's so ugly.

Brad

Marcel Holtmann wrote:
> Hi Henryk,
> 
> 
>>>So the best thing is too encode two or three full AVDTP frames in
>>>advance and have them ready to send. The sending can't be controlled
>>>be usleep(). We need a time that kicks in every whatever msec and
>>>makes us to transmit the next frame.
>>
>>That's what I would favour. According to the libc manual setitimer()
>>would be the function of choice, if nobody else has a better idea (RTC,
>>anyone?).
> 
> 
> so in general the time that a SBC frame is calculated for, is always the
> same if we don't change the parameters, right?
> 
> Using the ITIMER_REAL domain may works and since you can setup your
> timer in microseconds, then this would be the way to go.

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Index: a2play.c
===================================================================
RCS file: /cvsroot/bluetooth-alsa/btsco/a2play.c,v
retrieving revision 1.64
diff -u -b -B -w -p -r1.64 a2play.c
--- a2play.c	7 May 2005 02:43:00 -0000	1.64
+++ a2play.c	9 May 2005 06:30:36 -0000
@@ -56,6 +56,7 @@
 #define BUFS 1024
 
 static volatile int terminate = 0;
+static volatile int xmitpause = 0;
 static int cmdfd;
 
 struct sbc_frame_header sbc_info;
@@ -102,6 +103,16 @@ static void sig_term(int sig)
 	terminate = 1;
 }
 
+static void sig_alrm(int sig)
+{
+	struct sigaction sa;
+	memset(&sa, 0, sizeof(sa));
+	sa.sa_flags = SA_NOCLDSTOP;
+	sa.sa_handler = sig_alrm;
+	sigaction(SIGALRM, &sa, NULL);
+	xmitpause = 0;
+}
+
 // Usage
 static void usage()
 {
@@ -404,6 +415,8 @@ s_config was set from sbc_info before:
 
 int main(int argc, char *argv[])
 {
+	int timerset = 0;
+	struct itimerval itimer;
 	struct sigaction sa;
 	struct timeval start, end;
 	int streamfd;
@@ -619,6 +632,8 @@ int main(int argc, char *argv[])
 
 	timestamp = 0;
 
+	sig_alrm(0);
+
 	while (!terminate) {
 
 		// a2dp headers: avdtp p.45
@@ -698,8 +713,18 @@ int main(int argc, char *argv[])
 
 			memcpy(buf + sizeof(packet_header), &payload_header, sizeof(payload_header));
 			write(streamfd, buf, psize);
-			//printf("\nSending packet:%d, size %d no. of sbc frames:%d", seq_num, psize, payload_header.frame_count);
 
+			if(!timerset) {
+				timerset = 1;
+				itimer.it_interval.tv_sec = itimer.it_value.tv_sec = 0;
+				itimer.it_interval.tv_usec = itimer.it_value.tv_usec = (sleeptime*95)/100;
+				if(setitimer(ITIMER_REAL, &itimer, NULL)) printf("couldn't setitimer\n");
+			}
+
+			while(xmitpause) usleep(10);
+			xmitpause = 1;
+#if 0
+			//printf("\nSending packet:%d, size %d no. of sbc frames:%d", seq_num, psize, payload_header.frame_count);
 			pending++;
 
 			if (pending > 4) {
@@ -717,7 +742,7 @@ int main(int argc, char *argv[])
 				sleeptime = 0;
 				pending = 0;
 			}
-
+#endif
 			/* END: NONSPECAUDIO == FALSE */
 		}