add --pipe-size option to adjust output pipe size

In certain cases larger buffer will help to not lose packets
if the output pipeline goes through momentary stalls (e.g.
process in io wait when writing to disk).

bmd-streamer.c

@@ -48,6 +48,7 @@ struct encoding_parameters {
 	int8_t		input_source;
 	char *		exec_program;
 	int		respawn : 1;
+	int		pipe_sz;
 	int		src_x, src_y, src_width, src_height, dst_width, dst_height;
 };
 
@@ -633,7 +634,7 @@ static int pipe2(int pipefd[2], int flags)
 }
 #endif
 
-static int bmd_start_exec_program(struct blackmagic_device *bmd, char *exec_program)
+static int bmd_start_exec_program(struct blackmagic_device *bmd, int pipe_sz, char *exec_program)
 {
 	uint8_t ports[8];
 	char fmt[array_size(ports)*4];
@@ -653,6 +654,12 @@ static int bmd_start_exec_program(struct blackmagic_device *bmd, char *exec_prog
 	if (pipe2(pipefd, O_CLOEXEC) < 0)
 		return 0;
 
+	if (pipe_sz) {
+		if (fcntl(pipefd[0], F_SETPIPE_SZ, pipe_sz * 1024) < 0)
+			dlog(LOG_ERR, "%s: unable to set pipe size",
+			     bmd->name, ep.exec_program);
+	}
+
 	i = p = 0;
 	if (bmd->desc.idProduct != USB_PID_BMD_H264_PRO_RECORDER) {
 		envp[i++] = &tmp[p];
@@ -714,7 +721,7 @@ static void *bmd_pump_mpegts(void *ctx)
 			if (ep.exec_program) {
 				if (ep.respawn) {
 					bmd_kill_exec_program(bmd);
-					bmd_start_exec_program(bmd, ep.exec_program);
+					bmd_start_exec_program(bmd, ep.pipe_sz, ep.exec_program);
 				} else {
 					bmd->running = 0;
 				}
@@ -1031,7 +1038,7 @@ static void bmd_encoder_start(struct blackmagic_device *bmd)
 		goto error;
 	}
 
-	if (!bmd_start_exec_program(bmd, ep.exec_program)) {
+	if (!bmd_start_exec_program(bmd, ep.pipe_sz, ep.exec_program)) {
 		err = "start exec program";
 		goto error;
 	}
@@ -1321,6 +1328,7 @@ static int usage(void)
 		"	-S,--input-source	Set input source (component, sdi, hdmi,\n"
 		"				composite, s-video, or 0-4)\n"
 		"	-f,--firmware-dir	Directory for firmware images\n"
+		"	-z,--pipe-size		Set stream output pipe size in kB\n"
 		"	-x,--exec		Program to execute for each connected stream\n"
 		"	-R,--respawn		Restart execute program if it exits\n"
 		"	-s,--syslog		Log to syslog\n"
@@ -1352,6 +1360,7 @@ int main(int argc, char **argv)
 		{ "fps-divider",	required_argument, NULL, 'F' },
 		{ "firmware-dir",	required_argument, NULL, 'f' },
 		{ "input-source",	required_argument, NULL, 'S' },
+		{ "pipe-size",		required_argument, NULL, 'z' },
 		{ "exec",		required_argument, NULL, 'x' },
 		{ "respawn",		no_argument, NULL, 'R' },
 		{ "syslog",		no_argument, NULL, 's' },
@@ -1363,7 +1372,7 @@ int main(int argc, char **argv)
 		{ "dst-height",		required_argument, NULL, '5' },
 		{ NULL }
 	};
-	static const char short_options[] = "vk:K:a:P:L:bcBCF:f:S:x:Rs";
+	static const char short_options[] = "vk:K:a:P:L:bcBCF:f:S:z:x:Rs";
 
 	libusb_context *ctx;
 	libusb_hotplug_callback_handle cbhandle;
@@ -1409,6 +1418,7 @@ int main(int argc, char **argv)
 			if (i >= array_size(input_source_names)) i = -1;
 			ep.input_source = i;
 			break;
+		case 'z': ep.pipe_sz = atoi(optarg); break;
 		case '0': ep.src_x = atoi(optarg); break;
 		case '1': ep.src_y = atoi(optarg); break;
 		case '2': ep.src_width = atoi(optarg); break;