X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=vss.c;h=4a8aafa8d6e0c2ae239d09342ac10f3b08263828;hp=a8984a488421717b2173b94c4da3866aa6e2d766;hb=08be831b7b7e3e55d862eb988a604ccbde603403;hpb=5c07b5c17b25240495a0acee24ca6b03c8d81e72

diff --git a/vss.c b/vss.c
index a8984a48..4a8aafa8 100644
--- a/vss.c
+++ b/vss.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 1997-2009 Andre Noll <maan@systemlinux.org>
+ * Copyright (C) 1997-2011 Andre Noll <maan@systemlinux.org>
  *
  * Licensed under the GPL v2. For licencing details see COPYING.
  */
@@ -12,7 +12,6 @@
  */
 
 #include <regex.h>
-#include <dirent.h>
 #include <osl.h>
 
 #include "para.h"
@@ -26,8 +25,8 @@
 #include "net.h"
 #include "server.cmdline.h"
 #include "list.h"
-#include "vss.h"
 #include "send.h"
+#include "vss.h"
 #include "ipc.h"
 #include "fd.h"
 #include "sched.h"
@@ -86,7 +85,7 @@ struct vss_task {
 	/** Used by the scheduler. */
 	struct task task;
 	/** Pointer to the header of the mapped audio file. */
-	const char *header_buf;
+	char *header_buf;
 	/** Length of the audio file header. */
 	size_t header_len;
 	/** Time between audio file headers are sent. */
@@ -123,18 +122,31 @@ struct fec_group {
 	uint32_t num_chunks;
 	/** When the first chunk was sent. */
 	struct timeval start;
+	/** The duration of the full group. */
+	struct timeval duration;
 	/** The group duration divided by the number of slices. */
 	struct timeval slice_duration;
 	/** Group contains the audio file header that occupies that many slices. */
 	uint8_t num_header_slices;
+	/** Number of bytes per slice for this group. */
+	uint16_t slice_bytes;
+};
+
+/** A FEC client is always in one of these states. */
+enum fec_client_state {
+	FEC_STATE_NONE = 0,	/**< not initialized and not enabled */
+	FEC_STATE_DISABLED,	/**< temporarily disabled */
+	FEC_STATE_READY_TO_RUN	/**< initialized and enabled */
 };
 
 /**
  * Describes one connected FEC client.
  */
 struct fec_client {
-	/** If negative, this client is temporarily disabled. */
-	int error;
+	/** Current state of the client */
+	enum fec_client_state state;
+	/** The connected sender client (transport layer). */
+	struct sender_client *sc;
 	/** Parameters requested by the client. */
 	struct fec_client_parms *fcp;
 	/** Used by the core FEC code. */
@@ -155,10 +167,14 @@ struct fec_client {
 	struct timeval next_header_time;
 	/** Used for the last source pointer of an audio file. */
 	unsigned char *extra_src_buf;
+	/** Needed for the last slice of the audio file header. */
+	unsigned char *extra_header_buf;
 	/** Extra slices needed to store largest chunk + header. */
 	int num_extra_slices;
 	/** Contains the FEC-encoded data. */
 	unsigned char *enc_buf;
+	/** Maximal packet size. */
+	int mps;
 };
 
 /**
@@ -197,180 +213,405 @@ static void write_fec_header(struct fec_client *fc, struct vss_task *vsst)
 	write_u32(buf + 14, g->bytes);
 
 	write_u8(buf + 18, fc->current_slice_num);
-	write_u16(buf + 20, p->max_slice_bytes - FEC_HEADER_SIZE);
+	write_u8(buf + 19, 0); /* unused */
+	write_u16(buf + 20, g->slice_bytes);
 	write_u8(buf + 22, g->first_chunk? 0 : 1);
 	write_u8(buf + 23, vsst->header_len? 1 : 0);
-	memset(buf + 24, 0, 7);
+	memset(buf + 24, 0, 8);
 }
 
-static int need_audio_header(struct fec_client *fc, struct vss_task *vsst)
+static bool need_audio_header(struct fec_client *fc, struct vss_task *vsst)
 {
 	if (!mmd->current_chunk) {
 		tv_add(now, &vsst->header_interval, &fc->next_header_time);
-		return 0;
+		return false;
 	}
 	if (!vsst->header_buf)
-		return 0;
-	if (!vsst->header_len)
-		return 0;
-	if (fc->group.num && tv_diff(&fc->next_header_time, now, NULL) > 0)
-		return 0;
+		return false;
+	if (vsst->header_len == 0)
+		return false;
+	if (fc->group.num > 0) {
+		if (!fc->fcp->need_periodic_header)
+			return false;
+		if (tv_diff(&fc->next_header_time, now, NULL) > 0)
+			return false;
+	}
 	tv_add(now, &vsst->header_interval, &fc->next_header_time);
-	return 1;
+	return true;
+}
+
+static bool need_data_slices(struct fec_client *fc, struct vss_task *vsst)
+{
+	if (fc->group.num > 0)
+		return true;
+	if (!vsst->header_buf)
+		return true;
+	if (vsst->header_len == 0)
+		return true;
+	if (fc->fcp->need_periodic_header)
+		return true;
+	return false;
 }
 
-static int num_slices(long unsigned bytes, struct fec_client *fc, uint8_t *result)
+static int num_slices(long unsigned bytes, int max_payload, int rs)
 {
-	unsigned long m = fc->fcp->max_slice_bytes - FEC_HEADER_SIZE;
-	unsigned rv, redundant_slices = fc->fcp->slices_per_group
-		- fc->fcp->data_slices_per_group;
+	int ret;
 
-	if (!m)
-		return -E_BAD_CT;
-	rv = (bytes + m - 1) / m;
-	if (rv + redundant_slices > 255)
+	assert(max_payload > 0);
+	assert(rs > 0);
+	ret = DIV_ROUND_UP(bytes, max_payload);
+	if (ret + rs > 255)
 		return -E_BAD_CT;
-	*result = rv;
-	return 1;
+	return ret;
 }
 
-static void set_slice_duration(struct fec_client *fc, struct fec_group *g)
+/* set group start and group duration */
+static void set_group_timing(struct fec_client *fc, struct vss_task *vsst)
 {
-	struct timeval group_duration, *chunk_tv = vss_chunk_time();
+	struct fec_group *g = &fc->group;
+	struct timeval *chunk_tv = vss_chunk_time();
 
-	tv_scale(g->num_chunks, chunk_tv, &group_duration);
+	if (!need_data_slices(fc, vsst))
+		ms2tv(200, &g->duration);
+	else
+		tv_scale(g->num_chunks, chunk_tv, &g->duration);
 	tv_divide(fc->fcp->slices_per_group + fc->num_extra_slices,
-		&group_duration, &g->slice_duration);
+		&g->duration, &g->slice_duration);
 	PARA_DEBUG_LOG("durations (group/chunk/slice): %lu/%lu/%lu\n",
-		tv2ms(&group_duration), tv2ms(chunk_tv), tv2ms(&g->slice_duration));
+		tv2ms(&g->duration), tv2ms(chunk_tv), tv2ms(&g->slice_duration));
 }
 
-static int setup_next_fec_group(struct fec_client *fc, struct vss_task *vsst)
+static int initialize_fec_client(struct fec_client *fc, struct vss_task *vsst)
 {
-	int ret, i, k, data_slices;
-	size_t len;
-	const char *buf, *start_buf;
-	struct timeval tmp, *chunk_tv = vss_chunk_time();
-	struct fec_group *g = &fc->group;
-	unsigned slice_bytes = fc->fcp->max_slice_bytes - FEC_HEADER_SIZE;
-	uint32_t max_data_size;
-
-	assert(chunk_tv);
-	if (fc->first_stream_chunk < 0) {
-		uint8_t hs, ds; /* needed header/data slices */
-		uint8_t rs = fc->fcp->slices_per_group
-			- fc->fcp->data_slices_per_group; /* redundant slices */
-		int n;
+	int k, n, ret;
+	int hs, ds, rs; /* header/data/redundant slices */
+	struct fec_client_parms *fcp = fc->fcp;
 
-		ret = num_slices(vsst->header_len, fc, &hs);
+	/* set mps */
+	if (fcp->init_fec) {
+		/*
+		 * Set the maximum slice size to the Maximum Packet Size if the
+		 * transport protocol allows to determine this value. The user
+		 * can specify a slice size up to this value.
+		 */
+		ret = fcp->init_fec(fc->sc);
 		if (ret < 0)
 			return ret;
-		ret = num_slices(afh_get_largest_chunk_size(&mmd->afd.afhi),
-			fc, &ds);
+		fc->mps = ret;
+	} else
+		fc->mps = generic_max_transport_msg_size(fc->sc->fd);
+	if (fc->mps <= FEC_HEADER_SIZE)
+		return -ERRNO_TO_PARA_ERROR(EINVAL);
+
+	rs = fc->fcp->slices_per_group - fc->fcp->data_slices_per_group;
+	ret = num_slices(vsst->header_len, fc->mps - FEC_HEADER_SIZE, rs);
+	if (ret < 0)
+		return ret;
+	hs = ret;
+	ret = num_slices(mmd->afd.max_chunk_size, fc->mps - FEC_HEADER_SIZE, rs);
+	if (ret < 0)
+		return ret;
+	ds = ret;
+	if (fc->fcp->need_periodic_header)
+		k = hs + ds;
+	else
+		k = PARA_MAX(hs, ds);
+	if (k < fc->fcp->data_slices_per_group)
+		k = fc->fcp->data_slices_per_group;
+	fc->num_extra_slices = k - fc->fcp->data_slices_per_group;
+	n = k + rs;
+	fec_free(fc->parms);
+	ret = fec_new(k, n, &fc->parms);
+	if (ret < 0)
+		return ret;
+	PARA_INFO_LOG("mps: %d, k: %d, n: %d, extra slices: %d\n",
+		fc->mps, k, n, fc->num_extra_slices);
+	fc->src_data = para_realloc(fc->src_data, k * sizeof(char *));
+	fc->enc_buf = para_realloc(fc->enc_buf, fc->mps);
+	fc->extra_src_buf = para_realloc(fc->extra_src_buf, fc->mps);
+	fc->extra_header_buf = para_realloc(fc->extra_header_buf, fc->mps);
+
+	fc->state = FEC_STATE_READY_TO_RUN;
+	fc->next_header_time.tv_sec = 0;
+	fc->stream_start = *now;
+	fc->first_stream_chunk = mmd->current_chunk;
+	return 1;
+}
+
+static void vss_get_chunk(int chunk_num, struct vss_task *vsst,
+		char **buf, size_t *sz)
+{
+	/*
+	 * Chunk zero is special for header streams: It is the first portion of
+	 * the audio file which consists of the audio file header. It may be
+	 * arbitrary large due to embedded meta data. Audio format handlers may
+	 * replace the header by a stripped one with meta data omitted which is
+	 * of bounded size. We always use the stripped header for streaming
+	 * rather than the unmodified header (chunk zero).
+	 */
+	if (chunk_num == 0 && vsst->header_len > 0) {
+		*buf = vsst->header_buf; /* stripped header */
+		*sz = vsst->header_len;
+		return;
+	}
+	afh_get_chunk(chunk_num, &mmd->afd.afhi, vsst->map, (const char **)buf,
+		sz);
+}
+
+static void compute_group_size(struct vss_task *vsst, struct fec_group *g,
+		int max_bytes)
+{
+	char *buf;
+	size_t len;
+	int i, max_chunks = PARA_MAX(1LU, 150 / tv2ms(vss_chunk_time()));
+
+	if (g->first_chunk == 0) {
+		g->num_chunks = 1;
+		vss_get_chunk(0, vsst, &buf, &len);
+		g->bytes = len;
+		return;
+	}
+
+	g->num_chunks = 0;
+	g->bytes = 0;
+	/*
+	 * Include chunks into the group until the group duration is at least
+	 * 150ms.  For ogg and wma, a single chunk's duration (ogg page/wma
+	 * super frame) is already larger than 150ms, so a FEC group consists
+	 * of exactly one chunk for these audio formats.
+	 */
+	for (i = 0;; i++) {
+		int chunk_num = g->first_chunk + i;
+
+		if (g->bytes > 0 && i >= max_chunks) /* duration limit */
+			break;
+		if (chunk_num >= mmd->afd.afhi.chunks_total) /* eof */
+			break;
+		vss_get_chunk(chunk_num, vsst, &buf, &len);
+		if (g->bytes + len > max_bytes)
+			break;
+		/* Include this chunk */
+		g->bytes += len;
+		g->num_chunks++;
+	}
+	assert(g->num_chunks);
+}
+
+/*
+ * Compute the slice size of the next group.
+ *
+ * The FEC parameters n and k are fixed but the slice size varies per
+ * FEC group.  We'd like to choose slices as small as possible to avoid
+ * unnecessary FEC calculations but large enough to guarantee that the
+ * k data slices suffice to encode the header (if needed) and the data
+ * chunk(s).
+ *
+ * Once we know the payload of the next group, we define the number s
+ * of bytes per slice for this group by
+ *
+ * 	s = ceil(payload / k)
+ *
+ * However, for header streams, computing s is more complicated since no
+ * overlapping of header and data slices is possible. Hence we have k >=
+ * 2 and s must satisfy
+ *
+ * (*)	ceil(h / s) + ceil(d / s) <= k
+ *
+ * where h and d are payload of the header and the data chunk(s)
+ * respectively. In general there is no value for s such that (*)
+ * becomes an equality, for example if h = 4000, d = 5000 and k = 10.
+ *
+ * We use the following approach for computing a suitable value for s:
+ *
+ * Let
+ * 	k1 := ceil(k * min(h, d) / (h + d)),
+ * 	k2 := k - k1.
+ *
+ * Note that k >= 2 implies k1 > 0 and k2 > 0, so
+ *
+ * 	s := max(ceil(min(h, d) / k1), ceil(max(h, d) / k2))
+ *
+ * is well-defined. Inequality (*) holds for this value of s since k1
+ * slices suffice to store min(h, d) while k2 slices suffice to store
+ * max(h, d), i.e. the first addent of (*) is bounded by k1 and the
+ * second by k2.
+ *
+ * For the above example we obtain
+ *
+ * 	k1 = ceil(10 * 4000 / 9000) = 5, k2 = 5,
+ * 	s = max(4000 / 5, 5000 / 5) = 1000,
+ *
+ * which is optimal since a slice size of 999 bytes would already require
+ * 11 slices.
+ */
+static int compute_slice_size(struct fec_client *fc, struct vss_task *vsst)
+{
+	struct fec_group *g = &fc->group;
+	int k = fc->fcp->data_slices_per_group + fc->num_extra_slices;
+	int n = fc->fcp->slices_per_group + fc->num_extra_slices;
+	int ret, k1, k2, h, d, min, max, sum;
+	int max_slice_bytes = fc->mps - FEC_HEADER_SIZE;
+	int max_group_bytes;
+
+	if (!need_audio_header(fc, vsst)) {
+		max_group_bytes = k * max_slice_bytes;
+		g->num_header_slices = 0;
+		compute_group_size(vsst, g, max_group_bytes);
+		g->slice_bytes = DIV_ROUND_UP(g->bytes, k);
+		if (g->slice_bytes == 0)
+			g->slice_bytes = 1;
+		return 1;
+	}
+	if (!need_data_slices(fc, vsst)) {
+		g->bytes = 0;
+		g->num_chunks = 0;
+		g->slice_bytes = DIV_ROUND_UP(vsst->header_len, k);
+		g->num_header_slices = k;
+		return 1;
+	}
+	h = vsst->header_len;
+	max_group_bytes = (k - num_slices(h, max_slice_bytes, n - k))
+		* max_slice_bytes;
+	compute_group_size(vsst, g, max_group_bytes);
+	d = g->bytes;
+	if (d == 0) {
+		g->slice_bytes = DIV_ROUND_UP(h, k);
+		ret = num_slices(vsst->header_len, g->slice_bytes, n - k);
 		if (ret < 0)
 			return ret;
-		k = (int)hs + ds;
-		if (k > 255)
-			return -E_BAD_CT;
-		if (k < fc->fcp->data_slices_per_group)
-			k = fc->fcp->data_slices_per_group;
-		n = k + rs;
-		fc->num_extra_slices = k - fc->fcp->data_slices_per_group;
-		PARA_NOTICE_LOG("fec parms %d:%d:%d (%d extra slices)\n",
-			slice_bytes, k, n, fc->num_extra_slices);
-		fec_free(fc->parms);
-		fc->src_data = para_realloc(fc->src_data, k * sizeof(char *));
-		ret = fec_new(k, n, &fc->parms);
+		g->num_header_slices = ret;
+		return 1;
+	}
+	min = PARA_MIN(h, d);
+	max = PARA_MAX(h, d);
+	sum = h + d;
+	k1 = DIV_ROUND_UP(k * min, sum);
+	k2 = k - k1;
+	assert(k1 > 0);
+	assert(k2 > 0);
+
+	g->slice_bytes = PARA_MAX(DIV_ROUND_UP(min, k1), DIV_ROUND_UP(max, k2));
+	/*
+	 * This value of s := g->slice_bytes satisfies inequality (*) above,
+	 * but it might be larger than max_slice_bytes. However, we know that
+	 * max_slice_bytes are sufficient to store header and data, so:
+	 */
+	g->slice_bytes = PARA_MIN((int)g->slice_bytes, max_slice_bytes);
+
+	ret = num_slices(vsst->header_len, g->slice_bytes, n - k);
+	if (ret < 0)
+		return ret;
+	g->num_header_slices = ret;
+	return 1;
+}
+
+static int setup_next_fec_group(struct fec_client *fc, struct vss_task *vsst)
+{
+	int ret, i, k, n, data_slices;
+	size_t len;
+	char *buf, *p;
+	struct fec_group *g = &fc->group;
+
+	if (fc->state == FEC_STATE_NONE) {
+		ret = initialize_fec_client(fc, vsst);
 		if (ret < 0)
 			return ret;
-		fc->stream_start = *now;
-		fc->first_stream_chunk = mmd->current_chunk;
 		g->first_chunk = mmd->current_chunk;
 		g->num = 0;
+		g->start = *now;
 	} else {
-		k = fc->fcp->data_slices_per_group + fc->num_extra_slices;
-		/* use duration of the previous group for the timing of this group */
-		set_slice_duration(fc, g);
+		struct timeval tmp;
+		if (g->first_chunk + g->num_chunks >= mmd->afd.afhi.chunks_total)
+			return 0;
+		/*
+		 * Start and duration of this group depend only on the previous
+		 * group. Compute the new group start as g->start += g->duration.
+		 */
+		tmp = g->start;
+		tv_add(&tmp, &g->duration, &g->start);
+		set_group_timing(fc, vsst);
 		g->first_chunk += g->num_chunks;
 		g->num++;
 	}
-	if (g->first_chunk >= mmd->afd.afhi.chunks_total)
-		return 0;
-	if (need_audio_header(fc, vsst)) {
-		ret = num_slices(vsst->header_len, fc, &g->num_header_slices);
-		if (ret < 0)
-			return ret;
-	} else
-		g->num_header_slices = 0;
-	afh_get_chunk(g->first_chunk, &mmd->afd.afhi, vsst->map, &start_buf,
-		&len);
-	data_slices = k - g->num_header_slices;
-	assert(data_slices);
-	max_data_size = slice_bytes * data_slices;
-	g->bytes = 0;
-	for (i = g->first_chunk; i < mmd->afd.afhi.chunks_total; i++) {
-		afh_get_chunk(i, &mmd->afd.afhi, vsst->map, &buf, &len);
-		if (g->bytes + len > max_data_size)
-			break;
-		g->bytes += len;
-	}
-	g->num_chunks = i - g->first_chunk;
-	assert(g->num_chunks);
+	k = fc->fcp->data_slices_per_group + fc->num_extra_slices;
+	n = fc->fcp->slices_per_group + fc->num_extra_slices;
+
+	compute_slice_size(fc, vsst);
+	assert(g->slice_bytes > 0);
+	ret = num_slices(g->bytes, g->slice_bytes, n - k);
+	if (ret < 0)
+		return ret;
+	data_slices = ret;
+	assert(g->num_header_slices + data_slices <= k);
 	fc->current_slice_num = 0;
 	if (g->num == 0)
-		set_slice_duration(fc, g);
-
+		set_group_timing(fc, vsst);
 	/* setup header slices */
 	buf = vsst->header_buf;
 	for (i = 0; i < g->num_header_slices; i++) {
-		fc->src_data[i] = (const unsigned char *)buf;
-		buf += slice_bytes;
+		uint32_t payload_size;
+		if (buf + g->slice_bytes <= vsst->header_buf + vsst->header_len) {
+			fc->src_data[i] = (const unsigned char *)buf;
+			buf += g->slice_bytes;
+			continue;
+		}
+		/*
+		 * Can not use vss->header_buf for this slice as it
+		 * goes beyond the buffer. This slice will not be fully
+		 * used.
+		 */
+		payload_size = vsst->header_buf + vsst->header_len - buf;
+		memcpy(fc->extra_header_buf, buf, payload_size);
+		if (payload_size < g->slice_bytes)
+			memset(fc->extra_header_buf + payload_size, 0,
+				g->slice_bytes - payload_size);
+		fc->src_data[i] = fc->extra_header_buf;
+		assert(i == g->num_header_slices - 1);
 	}
 
-	/* setup data slices */
-	buf = start_buf;
-	for (i = g->num_header_slices; i < k; i++) {
-		if (buf + slice_bytes > vsst->map + mmd->size)
+	/*
+	 * Setup data slices. Note that for ogg streams chunk 0 points to a
+	 * buffer on the heap rather than to the mapped audio file.
+	 */
+	vss_get_chunk(g->first_chunk, vsst, &buf, &len);
+	for (p = buf; i < g->num_header_slices + data_slices; i++) {
+		if (p + g->slice_bytes > buf + g->bytes) {
 			/*
-			 * Can not use the memory mapped audio file for this
-			 * slice as it goes beyond the map. This slice will not
-			 * be fully used.
+			 * We must make a copy for this slice since using p
+			 * directly would exceed the buffer.
 			 */
+			uint32_t payload_size = buf + g->bytes - p;
+			assert(payload_size + FEC_HEADER_SIZE <= fc->mps);
+			memcpy(fc->extra_src_buf, p, payload_size);
+			if (payload_size < g->slice_bytes)
+				memset(fc->extra_src_buf + payload_size, 0,
+					g->slice_bytes - payload_size);
+			fc->src_data[i] = fc->extra_src_buf;
+			i++;
 			break;
-		fc->src_data[i] = (const unsigned char *)buf;
-		buf += slice_bytes;
+		}
+		fc->src_data[i] = (const unsigned char *)p;
+		p += g->slice_bytes;
 	}
 	if (i < k) {
-		uint32_t payload_size = vsst->map + mmd->size - buf;
-		memcpy(fc->extra_src_buf, buf, payload_size);
-		fc->src_data[i] = fc->extra_src_buf;
-		i++;
 		/* use arbitrary data for all remaining slices */
 		buf = vsst->map;
 		for (; i < k; i++)
 			fc->src_data[i] = (const unsigned char *)buf;
 	}
-	PARA_DEBUG_LOG("FEC group %d: %d chunks (%d - %d), "
-		"%d header slices, %d data slices\n",
+	PARA_DEBUG_LOG("FEC group %d: %d chunks (%d - %d), %d bytes\n",
 		g->num, g->num_chunks, g->first_chunk,
-		g->first_chunk + g->num_chunks - 1,
-		g->num_header_slices, data_slices
+		g->first_chunk + g->num_chunks - 1, g->bytes
+	);
+	PARA_DEBUG_LOG("slice_bytes: %d, %d header slices, %d data slices\n",
+		g->slice_bytes, g->num_header_slices, data_slices
 	);
-	/* set group start */
-	if (g->num != 0 && vsst->header_len != 0 && fc->first_stream_chunk == 0)
-		/* chunk #0 is the audio file header */
-		tv_scale(g->first_chunk - 1, chunk_tv, &tmp);
-	else
-		tv_scale(g->first_chunk - fc->first_stream_chunk,
-			chunk_tv, &tmp);
-	tv_add(&fc->stream_start, &tmp, &g->start);
 	return 1;
 }
 
 static int compute_next_fec_slice(struct fec_client *fc, struct vss_task *vsst)
 {
-	assert(fc->error >= 0);
-	if (fc->first_stream_chunk < 0 || fc->current_slice_num
+	if (fc->state == FEC_STATE_NONE || fc->current_slice_num
 			== fc->fcp->slices_per_group + fc->num_extra_slices) {
 		int ret = setup_next_fec_group(fc, vsst);
 		if (ret == 0)
@@ -378,14 +619,13 @@ static int compute_next_fec_slice(struct fec_client *fc, struct vss_task *vsst)
 		if (ret < 0) {
 			PARA_ERROR_LOG("%s\n", para_strerror(-ret));
 			PARA_ERROR_LOG("FEC client temporarily disabled\n");
-			fc->error = ret;
-			return fc->error;
+			fc->state = FEC_STATE_DISABLED;
+			return ret;
 		}
 	}
 	write_fec_header(fc, vsst);
 	fec_encode(fc->parms, fc->src_data, fc->enc_buf + FEC_HEADER_SIZE,
-		fc->current_slice_num,
-		fc->fcp->max_slice_bytes - FEC_HEADER_SIZE);
+		fc->current_slice_num, fc->group.slice_bytes);
 	return 1;
 }
 
@@ -408,38 +648,20 @@ size_t vss_get_fec_eof_packet(const char **buf)
 /**
  * Add one entry to the list of active fec clients.
  *
- * \param fcp Describes the fec parameters to be used for this client.
- * \param result An opaque pointer that must be used by remove the client later.
+ * \param sc  Generic sender_client data of the transport layer.
+ * \param fcp FEC parameters as supplied by the transport layer.
  *
- * \return Standard.
+ * \return Newly allocated fec_client struct.
  */
-int vss_add_fec_client(struct fec_client_parms *fcp, struct fec_client **result)
+struct fec_client *vss_add_fec_client(struct sender_client *sc,
+				      struct fec_client_parms *fcp)
 {
-	int ret;
-	struct fec_client *fc;
+	struct fec_client *fc = para_calloc(sizeof(*fc));
 
-	if (fcp->max_slice_bytes < FEC_HEADER_SIZE + fcp->data_slices_per_group)
-		return -ERRNO_TO_PARA_ERROR(EINVAL);
-	fc = para_calloc(sizeof(*fc));
+	fc->sc  = sc;
 	fc->fcp = fcp;
-	ret = fec_new(fcp->data_slices_per_group, fcp->slices_per_group,
-		&fc->parms);
-	if (ret < 0)
-		goto err;
-	fc->first_stream_chunk = -1; /* stream not yet started */
-	fc->src_data = para_malloc(fc->fcp->slices_per_group * sizeof(char *));
-	fc->enc_buf = para_calloc(fc->fcp->max_slice_bytes);
-	fc->num_extra_slices = 0;
-	fc->extra_src_buf = para_calloc(fc->fcp->max_slice_bytes);
-	fc->next_header_time.tv_sec = 0;
 	para_list_add(&fc->node, &fec_client_list);
-	*result = fc;
-	return 1;
-err:
-	fec_free(fc->parms);
-	free(fc);
-	*result = NULL;
-	return ret;
+	return fc;
 }
 
 /**
@@ -453,6 +675,7 @@ void vss_del_fec_client(struct fec_client *fc)
 	free(fc->src_data);
 	free(fc->enc_buf);
 	free(fc->extra_src_buf);
+	free(fc->extra_header_buf);
 	fec_free(fc->parms);
 	free(fc);
 }
@@ -469,7 +692,7 @@ static int next_slice_is_due(struct fec_client *fc, struct timeval *diff)
 	struct timeval tmp, next;
 	int ret;
 
-	if (fc->first_stream_chunk < 0)
+	if (fc->state == FEC_STATE_NONE)
 		return 1;
 	tv_scale(fc->current_slice_num, &fc->group.slice_duration, &tmp);
 	tv_add(&tmp, &fc->group.start, &next);
@@ -477,27 +700,6 @@ static int next_slice_is_due(struct fec_client *fc, struct timeval *diff)
 	return ret < 0? 1 : 0;
 }
 
-static void compute_slice_timeout(struct timeval *timeout)
-{
-	struct fec_client *fc;
-
-	assert(vss_playing());
-	list_for_each_entry(fc, &fec_client_list, node) {
-		struct timeval diff;
-
-		if (fc->error < 0)
-			continue;
-		if (next_slice_is_due(fc, &diff)) {
-			timeout->tv_sec = 0;
-			timeout->tv_usec = 0;
-			return;
-		}
-		/* timeout = min(timeout, diff) */
-		if (tv_diff(&diff, timeout, NULL) < 0)
-			*timeout = diff;
-	}
-}
-
 static void set_eof_barrier(struct vss_task *vsst)
 {
 	struct fec_client *fc;
@@ -508,7 +710,7 @@ static void set_eof_barrier(struct vss_task *vsst)
 	list_for_each_entry(fc, &fec_client_list, node) {
 		struct timeval group_duration;
 
-		if (fc->error < 0)
+		if (fc->state != FEC_STATE_READY_TO_RUN)
 			continue;
 		tv_scale(fc->group.num_chunks, chunk_tv, &group_duration);
 		if (tv_diff(&timeout, &group_duration, NULL) < 0)
@@ -588,42 +790,38 @@ static int chk_barrier(const char *bname, const struct timeval *barrier,
 	return -1;
 }
 
-/*
- * != NULL: timeout for next chunk
- * NULL: nothing to do
- */
-static struct timeval *vss_compute_timeout(struct vss_task *vsst)
+static void vss_compute_timeout(struct sched *s, struct vss_task *vsst)
 {
-	static struct timeval the_timeout;
-	struct timeval next_chunk;
+	struct timeval tv;
+	struct fec_client *fc;
 
-	if (vss_next() && vsst->map) {
-		/* only sleep a bit, nec*/
-		the_timeout.tv_sec = 0;
-		the_timeout.tv_usec = 100;
-		return &the_timeout;
-	}
-	if (chk_barrier("autoplay_delay", &vsst->autoplay_barrier,
-			&the_timeout, 1) < 0)
-		return &the_timeout;
-	if (chk_barrier("eof", &vsst->eof_barrier, &the_timeout, 1) < 0)
-		return &the_timeout;
-	if (chk_barrier("data send", &vsst->data_send_barrier,
-			&the_timeout, 1) < 0)
-		return &the_timeout;
 	if (!vss_playing() || !vsst->map)
-		return NULL;
+		return;
+	if (vss_next() && vsst->map) /* only sleep a bit, nec*/
+		return sched_request_timeout_ms(100, s);
+
+	/* Each of these barriers must have passed until we may proceed */
+	if (sched_request_barrier(&vsst->autoplay_barrier, s) == 1)
+		return;
+	if (sched_request_barrier(&vsst->eof_barrier, s) == 1)
+		return;
+	if (sched_request_barrier(&vsst->data_send_barrier, s) == 1)
+		return;
+	/*
+	 * Compute the select timeout as the minimal time until the next
+	 * chunk/slice is due for any client.
+	 */
 	compute_chunk_time(mmd->chunks_sent, &mmd->afd.afhi.chunk_tv,
-		&mmd->stream_start, &next_chunk);
-	if (chk_barrier("chunk", &next_chunk, &the_timeout, 0) >= 0) {
-		/* chunk is due or bof */
-		the_timeout.tv_sec = 0;
-		the_timeout.tv_usec = 0;
-		return &the_timeout;
+		&mmd->stream_start, &tv);
+	if (sched_request_barrier_or_min_delay(&tv, s) == 0)
+		return;
+	list_for_each_entry(fc, &fec_client_list, node) {
+		if (fc->state != FEC_STATE_READY_TO_RUN)
+			continue;
+		if (next_slice_is_due(fc, &tv))
+			return sched_min_delay(s);
+		sched_request_timeout(&tv, s);
 	}
-	/* compute min of current timeout and next slice time */
-	compute_slice_timeout(&the_timeout);
-	return &the_timeout;
 }
 
 static void vss_eof(struct vss_task *vsst)
@@ -634,10 +832,12 @@ static void vss_eof(struct vss_task *vsst)
 	if (mmd->new_vss_status_flags & VSS_NOMORE)
 		mmd->new_vss_status_flags = VSS_NEXT;
 	set_eof_barrier(vsst);
+	afh_free_header(vsst->header_buf, mmd->afd.audio_format_id);
+	vsst->header_buf = NULL;
 	para_munmap(vsst->map, mmd->size);
 	vsst->map = NULL;
 	mmd->chunks_sent = 0;
-	mmd->offset = 0;
+	//mmd->offset = 0;
 	mmd->afd.afhi.seconds_total = 0;
 	mmd->afd.afhi.chunk_tv.tv_sec = 0;
 	mmd->afd.afhi.chunk_tv.tv_usec = 0;
@@ -648,18 +848,6 @@ static void vss_eof(struct vss_task *vsst)
 	mmd->events++;
 }
 
-/**
- * Get the list of all supported audio formats.
- *
- * \return Aa space separated list of all supported audio formats
- * It is not allocated at runtime, i.e. there is no need to free
- * the returned string in the caller.
- */
-const char *supported_audio_formats(void)
-{
-	return SUPPORTED_AUDIO_FORMATS;
-}
-
 static int need_to_request_new_audio_file(struct vss_task *vsst)
 {
 	struct timeval diff;
@@ -678,6 +866,13 @@ static int need_to_request_new_audio_file(struct vss_task *vsst)
 	return 1;
 }
 
+static void set_mmd_offset(void)
+{
+	struct timeval offset;
+	tv_scale(mmd->current_chunk, &mmd->afd.afhi.chunk_tv, &offset);
+	mmd->offset = tv2ms(&offset);
+}
+
 /**
  * Compute the timeout for the main select-loop of the scheduler.
  *
@@ -695,7 +890,6 @@ static int need_to_request_new_audio_file(struct vss_task *vsst)
 static void vss_pre_select(struct sched *s, struct task *t)
 {
 	int i;
-	struct timeval *tv, diff;
 	struct vss_task *vsst = container_of(t, struct vss_task, task);
 
 	if (!vsst->map || vss_next() || vss_paused() || vss_repos()) {
@@ -703,10 +897,8 @@ static void vss_pre_select(struct sched *s, struct task *t)
 		for (i = 0; senders[i].name; i++)
 			if (senders[i].shutdown_clients)
 				senders[i].shutdown_clients();
-		list_for_each_entry_safe(fc, tmp, &fec_client_list, node) {
-			fc->first_stream_chunk = -1;
-			fc->error = 0;
-		}
+		list_for_each_entry_safe(fc, tmp, &fec_client_list, node)
+			fc->state = FEC_STATE_NONE;
 		mmd->stream_start.tv_sec = 0;
 		mmd->stream_start.tv_usec = 0;
 	}
@@ -722,6 +914,7 @@ static void vss_pre_select(struct sched *s, struct task *t)
 		mmd->chunks_sent = 0;
 		mmd->current_chunk = mmd->repos_request;
 		mmd->new_vss_status_flags &= ~VSS_REPOS;
+		set_mmd_offset();
 	}
 	if (need_to_request_new_audio_file(vsst)) {
 		PARA_DEBUG_LOG("ready and playing, but no audio file\n");
@@ -734,9 +927,7 @@ static void vss_pre_select(struct sched *s, struct task *t)
 			continue;
 		senders[i].pre_select(&s->max_fileno, &s->rfds, &s->wfds);
 	}
-	tv = vss_compute_timeout(vsst);
-	if (tv && tv_diff(tv, &s->timeout, &diff) < 0)
-		s->timeout = *tv;
+	vss_compute_timeout(s, vsst);
 }
 
 static int recv_afs_msg(int afs_socket, int *fd, uint32_t *code, uint32_t *data)
@@ -773,16 +964,24 @@ static int recv_afs_msg(int afs_socket, int *fd, uint32_t *code, uint32_t *data)
 	return 1;
 }
 
-static void recv_afs_result(struct vss_task *vsst)
+#ifndef MAP_POPULATE
+#define MAP_POPULATE 0
+#endif
+
+static void recv_afs_result(struct vss_task *vsst, fd_set *rfds)
 {
 	int ret, passed_fd, shmid;
 	uint32_t afs_code = 0, afs_data = 0;
 	struct stat statbuf;
 
-	vsst->afsss = AFS_SOCKET_READY;
+	if (!FD_ISSET(vsst->afs_socket, rfds))
+		return;
 	ret = recv_afs_msg(vsst->afs_socket, &passed_fd, &afs_code, &afs_data);
+	if (ret == -ERRNO_TO_PARA_ERROR(EAGAIN))
+		return;
 	if (ret < 0)
 		goto err;
+	vsst->afsss = AFS_SOCKET_READY;
 	PARA_DEBUG_LOG("fd: %d, code: %u, shmid: %u\n", passed_fd, afs_code,
 		afs_data);
 	ret = -E_NOFD;
@@ -803,8 +1002,8 @@ static void recv_afs_result(struct vss_task *vsst)
 	}
 	mmd->size = statbuf.st_size;
 	mmd->mtime = statbuf.st_mtime;
-	ret = para_mmap(mmd->size, PROT_READ, MAP_PRIVATE, passed_fd,
-		0, &vsst->map);
+	ret = para_mmap(mmd->size, PROT_READ, MAP_PRIVATE | MAP_POPULATE,
+		passed_fd, 0, &vsst->map);
 	if (ret < 0)
 		goto err;
 	close(passed_fd);
@@ -814,8 +1013,8 @@ static void recv_afs_result(struct vss_task *vsst)
 	mmd->events++;
 	mmd->num_played++;
 	mmd->new_vss_status_flags &= (~VSS_NEXT);
-	afh_get_header(&mmd->afd.afhi, vsst->map, &vsst->header_buf,
-		&vsst->header_len);
+	afh_get_header(&mmd->afd.afhi, mmd->afd.audio_format_id,
+		vsst->map, mmd->size, &vsst->header_buf, &vsst->header_len);
 	return;
 err:
 	free(mmd->afd.afhi.chunk_table);
@@ -848,7 +1047,7 @@ static void vss_send(struct vss_task *vsst)
 			&due, 1) < 0)
 		return;
 	list_for_each_entry_safe(fc, tmp_fc, &fec_client_list, node) {
-		if (fc->error < 0)
+		if (fc->state == FEC_STATE_DISABLED)
 			continue;
 		if (!next_slice_is_due(fc, NULL)) {
 			fec_active = 1;
@@ -857,10 +1056,9 @@ static void vss_send(struct vss_task *vsst)
 		if (compute_next_fec_slice(fc, vsst) <= 0)
 			continue;
 		PARA_DEBUG_LOG("sending %d:%d (%u bytes)\n", fc->group.num,
-			fc->current_slice_num, fc->fcp->max_slice_bytes);
-		fc->fcp->send((char *)fc->enc_buf,
-			fc->fcp->max_slice_bytes,
-			fc->fcp->private_data);
+			fc->current_slice_num, fc->group.slice_bytes);
+		fc->fcp->send_fec(fc->sc, (char *)fc->enc_buf,
+			fc->group.slice_bytes + FEC_HEADER_SIZE);
 		fc->current_slice_num++;
 		fec_active = 1;
 	}
@@ -872,29 +1070,45 @@ static void vss_send(struct vss_task *vsst)
 	compute_chunk_time(mmd->chunks_sent, &mmd->afd.afhi.chunk_tv,
 		&mmd->stream_start, &due);
 	if (tv_diff(&due, now, NULL) <= 0) {
-		const char *buf;
+		char *buf;
 		size_t len;
 
 		if (!mmd->chunks_sent) {
-			struct timeval tmp;
 			mmd->stream_start = *now;
-			tv_scale(mmd->current_chunk, &mmd->afd.afhi.chunk_tv, &tmp);
-			mmd->offset = tv2ms(&tmp);
 			mmd->events++;
+			set_mmd_offset();
 		}
 		/*
 		 * We call the send function also in case of empty chunks as
 		 * they might have still some data queued which can be sent in
 		 * this case.
 		 */
-		afh_get_chunk(mmd->current_chunk, &mmd->afd.afhi, vsst->map,
-			&buf, &len);
+		vss_get_chunk(mmd->current_chunk, vsst, &buf, &len);
 		for (i = 0; senders[i].name; i++) {
 			if (!senders[i].send)
 				continue;
 			senders[i].send(mmd->current_chunk, mmd->chunks_sent,
 				buf, len, vsst->header_buf, vsst->header_len);
 		}
+		/*
+		 * Prefault next chunk(s)
+		 *
+		 * If the backing device of the memory-mapped audio file is
+		 * slow and read-ahead is turned off or prevented for some
+		 * reason, e.g. due to memory pressure, it may take much longer
+		 * than the chunk interval to get the next chunk on the wire,
+		 * causing buffer underruns on the client side. Mapping the
+		 * file with MAP_POPULATE seems to help a bit, but it does not
+		 * eliminate the delays completely. Moreover, it is supported
+		 * only on Linux. So we do our own read-ahead here.
+		 */
+		if (mmd->current_chunk > 0) { /* chunk 0 might be on the heap */
+			buf += len;
+			for (i = 0; i < 5 && buf < vsst->map + mmd->size; i++) {
+				__a_unused volatile char x = *buf;
+				buf += 4096;
+			}
+		}
 		mmd->chunks_sent++;
 		mmd->current_chunk++;
 	}
@@ -910,14 +1124,17 @@ static void vss_post_select(struct sched *s, struct task *t)
 		int num = mmd->sender_cmd_data.cmd_num,
 			sender_num = mmd->sender_cmd_data.sender_num;
 
-		if (senders[sender_num].client_cmds[num])
-			senders[sender_num].client_cmds[num](&mmd->sender_cmd_data);
+		if (senders[sender_num].client_cmds[num]) {
+			ret = senders[sender_num].client_cmds[num]
+				(&mmd->sender_cmd_data);
+			if (ret < 0)
+				PARA_ERROR_LOG("%s\n", para_strerror(-ret));
+		}
 		mmd->sender_cmd_data.cmd_num = -1;
 	}
-	if (vsst->afsss != AFS_SOCKET_CHECK_FOR_WRITE) {
-		if (FD_ISSET(vsst->afs_socket, &s->rfds))
-			recv_afs_result(vsst);
-	} else if (FD_ISSET(vsst->afs_socket, &s->wfds)) {
+	if (vsst->afsss != AFS_SOCKET_CHECK_FOR_WRITE)
+		recv_afs_result(vsst, &s->rfds);
+	else if (FD_ISSET(vsst->afs_socket, &s->wfds)) {
 		PARA_NOTICE_LOG("requesting new fd from afs\n");
 		ret = send_buffer(vsst->afs_socket, "new");
 		if (ret < 0)
@@ -976,5 +1193,6 @@ void init_vss_task(int afs_socket)
 		tv_add(&vsst->autoplay_barrier, &vsst->announce_tv,
 			&vsst->data_send_barrier);
 	}
+	sprintf(vsst->task.status, "vss task");
 	register_task(&vsst->task);
 }