diff --git a/src/Makefile.am b/src/Makefile.am
index 99ebf57c9..b7c605f1a 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -5,6 +5,7 @@ bin_PROGRAMS = bluealsa
 SUBDIRS = asound
 
 bluealsa_SOURCES = \
+	shared/ffb.c \
 	shared/log.c \
 	shared/rt.c \
 	at.c \
diff --git a/src/io.c b/src/io.c
index d211d5ad1..675778b12 100644
--- a/src/io.c
+++ b/src/io.c
@@ -36,6 +36,7 @@
 #include "bluealsa.h"
 #include "transport.h"
 #include "utils.h"
+#include "shared/ffb.h"
 #include "shared/log.h"
 #include "shared/rt.h"
 
@@ -978,22 +979,27 @@ void *io_thread_sco(void *arg) {
 	pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, NULL);
 	pthread_cleanup_push(CANCEL_ROUTINE(transport_pthread_cleanup), t);
 
-	/* this buffer has to be bigger than SCO MTU */
-	const size_t buffer_size = 512;
-	int16_t *buffer = malloc(buffer_size);
+	/* buffers for transferring data to and fro SCO socket */
+	struct ffb bt_in = { 0 };
+	struct ffb bt_out = { 0 };
+	pthread_cleanup_push(CANCEL_ROUTINE(ffb_free), &bt_in);
+	pthread_cleanup_push(CANCEL_ROUTINE(ffb_free), &bt_out);
 
-	pthread_cleanup_push(CANCEL_ROUTINE(free), buffer);
-
-	if (buffer == NULL) {
-		error("Couldn't create data buffers: %s", strerror(ENOMEM));
+	/* these buffers shall be bigger than the SCO MTU */
+	if (ffb_init(&bt_in, 128) == -1 || ffb_init(&bt_out, 128) == -1) {
+		error("Couldn't create data buffer: %s", strerror(ENOMEM));
 		goto fail;
 	}
 
 	struct asrsync asrs = { .frames = 0 };
 	struct pollfd pfds[] = {
 		{ t->event_fd, POLLIN, 0 },
+		/* SCO socket */
 		{ -1, POLLIN, 0 },
+		{ -1, POLLOUT, 0 },
+		/* PCM FIFO */
 		{ -1, POLLIN, 0 },
+		{ -1, POLLOUT, 0 },
 	};
 
 	debug("Starting IO loop: %s",
@@ -1001,8 +1007,25 @@ void *io_thread_sco(void *arg) {
 	for (;;) {
 		pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL);
 
-		pfds[1].fd = t->sco.mic_pcm.fd != -1 ? t->bt_fd : -1;
-		pfds[2].fd = t->sco.spk_pcm.fd;
+		/* fresh-start for file descriptors polling */
+		pfds[1].fd = pfds[2].fd = -1;
+		pfds[3].fd = pfds[4].fd = -1;
+
+		switch (t->codec) {
+		case HFP_CODEC_CVSD:
+		default:
+			if (ffb_len_in(&bt_in) >= t->mtu_read)
+				pfds[1].fd = t->bt_fd;
+			if (ffb_len_out(&bt_out) >= t->mtu_write)
+				pfds[2].fd = t->bt_fd;
+			if (ffb_len_in(&bt_out) >= t->mtu_write)
+				pfds[3].fd = t->sco.spk_pcm.fd;
+			if (ffb_len_out(&bt_in) >= t->mtu_read)
+				pfds[4].fd = t->sco.mic_pcm.fd;
+		}
+
+		if (t->sco.mic_pcm.fd == -1)
+			pfds[1].fd = -1;
 
 		if (poll(pfds, sizeof(pfds) / sizeof(*pfds), -1) == -1) {
 			error("Transport poll error: %s", strerror(errno));
@@ -1052,15 +1075,25 @@ void *io_thread_sco(void *arg) {
 			asrsync_init(asrs, transport_get_sampling(t));
 
 		if (pfds[1].revents & POLLIN) {
+			/* dispatch incoming SCO data */
 
+			uint8_t *buffer;
+			size_t buffer_len;
 			ssize_t len;
 
-retry_sco:
+			switch (t->codec) {
+			case HFP_CODEC_CVSD:
+			default:
+				buffer = bt_in.tail;
+				buffer_len = ffb_len_in(&bt_in);
+			}
+
+retry_sco_read:
 			errno = 0;
-			if ((len = read(pfds[1].fd, buffer, buffer_size)) <= 0)
+			if ((len = read(pfds[1].fd, buffer, buffer_len)) <= 0)
 				switch (errno) {
 				case EINTR:
-					goto retry_sco;
+					goto retry_sco_read;
 				case 0:
 				case ECONNABORTED:
 				case ECONNRESET:
@@ -1071,19 +1104,68 @@ void *io_thread_sco(void *arg) {
 					continue;
 				}
 
-			if (t->sco.mic_muted)
-				snd_pcm_scale_s16le(buffer, len / sizeof(int16_t), 1, 0, 0);
+			switch (t->codec) {
+			case HFP_CODEC_CVSD:
+			default:
+				ffb_seek(&bt_in, len);
+			}
 
-			write(t->sco.mic_pcm.fd, buffer, len);
 		}
 		else if (pfds[1].revents & (POLLERR | POLLHUP)) {
 			debug("SCO poll error status: 0x%x", pfds[1].revents);
 			transport_release_bt_sco(t);
 		}
 
-		if (pfds[2].revents & POLLIN) {
+		if (pfds[2].revents & POLLOUT) {
+			/* write-out SCO data */
+
+			uint8_t *buffer;
+			size_t buffer_len;
+			ssize_t len;
+
+			switch (t->codec) {
+			case HFP_CODEC_CVSD:
+			default:
+				buffer = bt_out.data;
+				buffer_len = t->mtu_write;
+			}
 
-			ssize_t samples = t->mtu_write / sizeof(int16_t);
+retry_sco_write:
+			errno = 0;
+			if ((len = write(pfds[2].fd, buffer, buffer_len)) <= 0)
+				switch (errno) {
+				case EINTR:
+					goto retry_sco_write;
+				case 0:
+				case ECONNABORTED:
+				case ECONNRESET:
+					transport_release_bt_sco(t);
+					continue;
+				default:
+					error("SCO write error: %s", strerror(errno));
+					continue;
+				}
+
+			switch (t->codec) {
+			case HFP_CODEC_CVSD:
+			default:
+				ffb_rewind(&bt_out, len);
+			}
+
+		}
+
+		if (pfds[3].revents & POLLIN) {
+			/* dispatch incoming PCM data */
+
+			int16_t *buffer;
+			ssize_t samples;
+
+			switch (t->codec) {
+			case HFP_CODEC_CVSD:
+			default:
+				buffer = (int16_t *)bt_out.tail;
+				samples = ffb_len_in(&bt_out) / sizeof(int16_t);
+			}
 
 			/* read data from the FIFO - this function will block */
 			if ((samples = io_thread_read_pcm(&t->sco.spk_pcm, buffer, samples)) <= 0) {
@@ -1095,10 +1177,42 @@ void *io_thread_sco(void *arg) {
 			if (t->sco.spk_muted)
 				snd_pcm_scale_s16le(buffer, samples, 1, 0, 0);
 
-			write(t->bt_fd, buffer, samples * sizeof(int16_t));
+			switch (t->codec) {
+			case HFP_CODEC_CVSD:
+			default:
+				ffb_seek(&bt_out, samples * sizeof(int16_t));
+			}
+
 		}
-		else if (pfds[2].revents & (POLLERR | POLLHUP)) {
-			debug("PCM poll error status: 0x%x", pfds[2].revents);
+		else if (pfds[3].revents & (POLLERR | POLLHUP)) {
+			debug("PCM poll error status: 0x%x", pfds[3].revents);
+		}
+
+		if (pfds[4].revents & POLLOUT) {
+			/* write-out PCM data */
+
+			int16_t *buffer;
+			ssize_t samples;
+
+			switch (t->codec) {
+			case HFP_CODEC_CVSD:
+			default:
+				buffer = (int16_t *)bt_in.data;
+				samples = ffb_len_out(&bt_in) / sizeof(int16_t);
+			}
+
+			if (t->sco.mic_muted)
+				snd_pcm_scale_s16le(buffer, samples, 1, 0, 0);
+
+			if (io_thread_write_pcm(&t->sco.mic_pcm, buffer, samples) == -1)
+				error("FIFO write error: %s", strerror(errno));
+
+			switch (t->codec) {
+			case HFP_CODEC_CVSD:
+			default:
+				ffb_rewind(&bt_in, samples * sizeof(int16_t));
+			}
+
 		}
 
 		/* keep data transfer at a constant bit rate */
@@ -1111,5 +1225,6 @@ void *io_thread_sco(void *arg) {
 	pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, NULL);
 	pthread_cleanup_pop(1);
 	pthread_cleanup_pop(1);
+	pthread_cleanup_pop(1);
 	return NULL;
 }
diff --git a/src/shared/ffb.c b/src/shared/ffb.c
new file mode 100644
index 000000000..13bb6125e
--- /dev/null
+++ b/src/shared/ffb.c
@@ -0,0 +1,41 @@
+/*
+ * BlueALSA - ffb.c
+ * Copyright (c) 2016-2017 Arkadiusz Bokowy
+ *
+ * This file is a part of bluez-alsa.
+ *
+ * This project is licensed under the terms of the MIT license.
+ *
+ */
+
+#include "shared/ffb.h"
+
+#include <stdlib.h>
+
+
+/**
+ * Allocated resources for FIFO-like buffer.
+ *
+ * @param ffb Pointer to the buffer structure which should be initialized.
+ * @param size Size of the buffer in bytes.
+ * @return On success this function returns 0. Otherwise, -1 is returned and
+ *	 errno is set to indicate the error. */
+int ffb_init(struct ffb *ffb, size_t size) {
+	if ((ffb->data = ffb->tail = malloc(size)) == NULL)
+		return -1;
+	ffb->size = size;
+	return 0;
+}
+
+/**
+ * Free resources allocated by the ffb_init().
+ *
+ * @param ffb Pointer to initialized buffer structure. */
+void ffb_free(struct ffb *ffb) {
+	if (ffb->data == NULL)
+		return;
+	free(ffb->data);
+	ffb->data = NULL;
+	ffb->tail = NULL;
+	ffb->size = 0;
+}
diff --git a/src/shared/ffb.h b/src/shared/ffb.h
new file mode 100644
index 000000000..9021d6142
--- /dev/null
+++ b/src/shared/ffb.h
@@ -0,0 +1,40 @@
+/*
+ * BlueALSA - ffb.h
+ * Copyright (c) 2016-2017 Arkadiusz Bokowy
+ *
+ * This file is a part of bluez-alsa.
+ *
+ * This project is licensed under the terms of the MIT license.
+ *
+ */
+
+#ifndef BLUEALSA_SHARED_FFB_H_
+#define BLUEALSA_SHARED_FFB_H_
+
+#include <stddef.h>
+#include <string.h>
+
+/**
+ * Convenience wrapper for FIFO-like buffer. */
+struct ffb {
+	/* pointer to the allocated memory block */
+	unsigned char *data;
+	/* pointer to the end of data */
+	unsigned char *tail;
+	/* size of the buffer */
+	size_t size;
+};
+
+int ffb_init(struct ffb *ffb, size_t size);
+void ffb_free(struct ffb *ffb);
+
+#define ffb_len_in(p) ((p)->size - ffb_len_out(p))
+#define ffb_len_out(p) ((size_t)((p)->tail - (p)->data))
+
+#define ffb_seek(p, len) ((p)->tail += len)
+#define ffb_rewind(p, len) do { \
+		memmove((p)->data, (p)->data + (len), ffb_len_out(p) - (len)); \
+		(p)->tail -= len; \
+	} while (0)
+
+#endif
diff --git a/test/inc/test.inc b/test/inc/test.inc
index 98c86b1ad..b2a5cba7d 100644
--- a/test/inc/test.inc
+++ b/test/inc/test.inc
@@ -25,10 +25,11 @@ static char test_error_msg[512];
 static char test_warn_msg[512];
 static char test_info_msg[512];
 
-#define test_run(f) \
-	test_error_count = test_warn_count = test_info_count = 0; \
-	*test_error_msg = *test_warn_msg = *test_info_msg = '\0'; \
-	assert(!f())
+#define test_run(f) do { \
+		test_error_count = test_warn_count = test_info_count = 0; \
+		*test_error_msg = *test_warn_msg = *test_info_msg = '\0'; \
+		assert(!f()); \
+	} while (0)
 
 void error(const char *format, ...) {
 	va_list ap;
diff --git a/test/test-at.c b/test/test-at.c
index 8a0fc8c5b..88edfd90f 100644
--- a/test/test-at.c
+++ b/test/test-at.c
@@ -8,7 +8,6 @@
  *
  */
 
-#include <stdlib.h>
 #include "inc/test.inc"
 #include "../src/at.c"
 
@@ -105,5 +104,5 @@ int main(void) {
 	/* parse +CIND invalid response */
 	assert(at_parse_cind("(incorrect,1-2)", indmap) == -1);
 
-	return EXIT_SUCCESS;
+	return 0;
 }
diff --git a/test/test-io.c b/test/test-io.c
index 4cc238024..d4be542ee 100644
--- a/test/test-io.c
+++ b/test/test-io.c
@@ -18,6 +18,7 @@
 #include "../src/rfcomm.c"
 #include "../src/transport.c"
 #include "../src/utils.c"
+#include "../src/shared/ffb.c"
 #include "../src/shared/rt.c"
 
 static const a2dp_sbc_t config_sbc_44100_joint_stereo = {
@@ -174,10 +175,8 @@ int test_a2dp_sbc_encoding(void) {
 }
 
 int main(void) {
-
 	test_run(test_a2dp_sbc_invalid_setup);
 	test_run(test_a2dp_sbc_decoding);
 	test_run(test_a2dp_sbc_encoding);
-
-	return EXIT_SUCCESS;
+	return 0;
 }
diff --git a/test/test-pcm.c b/test/test-pcm.c
index 05d06f738..bf558978f 100644
--- a/test/test-pcm.c
+++ b/test/test-pcm.c
@@ -16,6 +16,7 @@
 #include <alsa/asoundlib.h>
 #include "inc/sine.inc"
 #include "inc/test.inc"
+#include "../src/shared/ffb.c"
 #include "../src/shared/log.h"
 
 
diff --git a/test/test-server.c b/test/test-server.c
index f4a617834..3f1dd0dbf 100644
--- a/test/test-server.c
+++ b/test/test-server.c
@@ -28,13 +28,14 @@
 #define io_thread_a2dp_sink_sbc _io_thread_a2dp_sink_sbc
 #define io_thread_a2dp_source_sbc _io_thread_a2dp_source_sbc
 #include "../src/io.c"
-#include "../src/rfcomm.c"
 #undef io_thread_a2dp_sink_sbc
 #undef io_thread_a2dp_source_sbc
+#include "../src/rfcomm.c"
 #define transport_acquire_bt_a2dp _transport_acquire_bt_a2dp
 #include "../src/transport.c"
 #undef transport_acquire_bt_a2dp
 #include "../src/utils.c"
+#include "../src/shared/ffb.c"
 #include "../src/shared/rt.c"
 
 static const a2dp_sbc_t cconfig = {
diff --git a/test/test-utils.c b/test/test-utils.c
index 5f5282f44..61335b3d5 100644
--- a/test/test-utils.c
+++ b/test/test-utils.c
@@ -10,6 +10,7 @@
 
 #include "inc/test.inc"
 #include "../src/utils.c"
+#include "../src/shared/ffb.c"
 #include "../src/shared/rt.c"
 
 int test_dbus_profile_object_path(void) {
@@ -127,11 +128,34 @@ int test_difftimespec(void) {
 	return 0;
 }
 
-int main(void) {
+int test_fifo_buffer(void) {
+
+	struct ffb ffb = { 0 };
+
+	assert(ffb_init(&ffb, 64) == 0);
+	assert(ffb.data == ffb.tail);
+	assert(ffb.size == 64);
+
+	memcpy(ffb.data, "1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ", 36);
+	ffb_seek(&ffb, 36);
+
+	assert(ffb_len_in(&ffb) == 64 - 36);
+	assert(ffb_len_out(&ffb) == 36);
+	assert(ffb.tail[-1] == 'Z');
+
+	ffb_rewind(&ffb, 15);
+	assert(ffb_len_in(&ffb) == 64 - (36 - 15));
+	assert(ffb_len_out(&ffb) == 36 - 15);
+	assert(memcmp(ffb.data, "FGHIJKLMNOPQRSTUVWXYZ", ffb_len_out(&ffb)) == 0);
+	assert(ffb.tail[-1] == 'Z');
 
+	return 0;
+}
+
+int main(void) {
 	test_run(test_dbus_profile_object_path);
 	test_run(test_pcm_scale_s16le);
 	test_run(test_difftimespec);
-
-	return EXIT_SUCCESS;
+	test_run(test_fifo_buffer);
+	return 0;
 }