Block on frameout if the hardware has enough samples to complete a frame.

Fixes some problems with skipping audio in elaborate scenarios involving
multiple codecs by making codec_dahdi operate in a more synchronous
fashion similar to codec_g729. This change also fixes the use of file
conversion tools from Asterisk's CLI. This change may cause the thread
responsible for transcoding audio to block briefly (Shaun Ruffell describes
this as 'several milliseconds') while waiting for the hardware transcoder.

(closes issue ASTERISK-19643)
reported by: Shaun Ruffell
Patches:
	0001-codec_dahdi-Block-on-frameout-the-hardware-has-enoug.patch
	uploaded by Shaun Ruffell (license 5417)


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@365989 65c4cc65-6c06-0410-ace0-fbb531ad65f3

codecs/codec_dahdi.c

@@ -56,6 +56,7 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 
 #define G723_SAMPLES 240
 #define G729_SAMPLES 160
+#define ULAW_SAMPLES 160
 
 static struct channel_usage {
 	int total;
@@ -89,6 +90,7 @@ struct codec_dahdi_pvt {
 	unsigned int fake:2;
 	uint16_t required_samples;
 	uint16_t samples_in_buffer;
+	uint16_t samples_written_to_hardware;
 	uint8_t ulaw_buffer[1024];
 };
 
@@ -160,7 +162,6 @@ static char *handle_cli_transcoder_show(struct ast_cli_entry *e, int cmd, struct
 static void dahdi_write_frame(struct codec_dahdi_pvt *dahdip, const uint8_t *buffer, const ssize_t count)
 {
 	int res;
-	struct pollfd p = {0};
 	if (!count) return;
 	res = write(dahdip->fd, buffer, count);
 	if (option_verbose > 10) {
@@ -171,9 +172,6 @@ static void dahdi_write_frame(struct codec_dahdi_pvt *dahdip, const uint8_t *buf
 			ast_log(LOG_ERROR, "Requested write of %zd bytes, but only wrote %d bytes.\n", count, res);
 		}
 	}
-	p.fd = dahdip->fd;
-	p.events = POLLOUT;
-	res = poll(&p, 1, 50);
 }
 
 static int dahdi_encoder_framein(struct ast_trans_pvt *pvt, struct ast_frame *f)
@@ -206,8 +204,9 @@ static int dahdi_encoder_framein(struct ast_trans_pvt *pvt, struct ast_frame *f)
 		dahdip->samples_in_buffer += f->samples;
 	}
 
-	while (dahdip->samples_in_buffer > dahdip->required_samples) {
+	while (dahdip->samples_in_buffer >= dahdip->required_samples) {
 		dahdi_write_frame(dahdip, dahdip->ulaw_buffer, dahdip->required_samples);
+		dahdip->samples_written_to_hardware += dahdip->required_samples;
 		dahdip->samples_in_buffer -= dahdip->required_samples;
 		if (dahdip->samples_in_buffer) {
 			/* Shift any remaining bytes down. */
@@ -220,6 +219,14 @@ static int dahdi_encoder_framein(struct ast_trans_pvt *pvt, struct ast_frame *f)
 	return -1;
 }
 
+static void dahdi_wait_for_packet(int fd)
+{
+	struct pollfd p = {0};
+	p.fd = fd;
+	p.events = POLLIN;
+	poll(&p, 1, 10);
+}
+
 static struct ast_frame *dahdi_encoder_frameout(struct ast_trans_pvt *pvt)
 {
 	struct codec_dahdi_pvt *dahdip = pvt->pvt;
@@ -243,6 +250,10 @@ static struct ast_frame *dahdi_encoder_frameout(struct ast_trans_pvt *pvt)
 		return NULL;
 	}
 
+	if (dahdip->samples_written_to_hardware >= dahdip->required_samples) {
+		dahdi_wait_for_packet(dahdip->fd);
+	}
+
 	res = read(dahdip->fd, pvt->outbuf.c + pvt->datalen, pvt->t->buf_size - pvt->datalen);
 	if (-1 == res) {
 		if (EWOULDBLOCK == errno) {
@@ -262,6 +273,10 @@ static struct ast_frame *dahdi_encoder_frameout(struct ast_trans_pvt *pvt)
 		pvt->f.data.ptr = pvt->outbuf.c;
 		pvt->f.samples = ast_codec_get_samples(&pvt->f);
 
+		dahdip->samples_written_to_hardware =
+		  (dahdip->samples_written_to_hardware >= pvt->f.samples) ?
+		     dahdip->samples_written_to_hardware - pvt->f.samples : 0;
+
 		pvt->samples = 0;
 		pvt->datalen = 0;
 		return ast_frisolate(&pvt->f);
@@ -288,6 +303,7 @@ static int dahdi_decoder_framein(struct ast_trans_pvt *pvt, struct ast_frame *f)
 		}
 	}
 	dahdi_write_frame(dahdip, f->data.ptr, f->datalen);
+	dahdip->samples_written_to_hardware += f->samples;
 	pvt->samples += f->samples;
 	pvt->datalen = 0;
 	return -1;
@@ -315,6 +331,10 @@ static struct ast_frame *dahdi_decoder_frameout(struct ast_trans_pvt *pvt)
 		return NULL;
 	}
 
+	if (dahdip->samples_written_to_hardware >= ULAW_SAMPLES) {
+		dahdi_wait_for_packet(dahdip->fd);
+	}
+
 	/* Let's check to see if there is a new frame for us.... */
 	if (dahdip->softslin) {
 		res = read(dahdip->fd, dahdip->ulaw_buffer, sizeof(dahdip->ulaw_buffer));
@@ -346,6 +366,9 @@ static struct ast_frame *dahdi_decoder_frameout(struct ast_trans_pvt *pvt)
 		pvt->f.data.ptr = pvt->outbuf.c;
 		pvt->f.samples = res;
 		pvt->samples = 0;
+		dahdip->samples_written_to_hardware =
+			(dahdip->samples_written_to_hardware >= res) ?
+			        dahdip->samples_written_to_hardware - res : 0;
 
 		return ast_frisolate(&pvt->f);
 	}