avformat: Add ZeroMQ as a protocol

When ffmpeg was streaming, multiple clients were only supported by using a
multicast destination address. An alternative was to stream to a server which
re-distributes the content. This commit adds ZeroMQ as a protocol, which allows
multiple clients to connect to a single ffmpeg instance.

Signed-off-by: Marton Balint <cus@passwd.hu>

1 files changed, 199 insertions, 0 deletions

diff --git a/libavformat/libzmq.c b/libavformat/libzmq.c
new file mode 100644
index 0000000000..d86488293f
--- /dev/null
+++ b/libavformat/libzmq.c
@@ -0,0 +1,199 @@
+/*
+ * ZeroMQ Protocol
+ * Copyright (c) 2019 Andriy Gelman
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <zmq.h>
+#include "url.h"
+#include "network.h"
+#include "libavutil/avstring.h"
+#include "libavutil/opt.h"
+#include "libavutil/time.h"
+
+#define ZMQ_STRERROR zmq_strerror(zmq_errno())
+
+typedef struct ZMQContext {
+    const AVClass *class;
+    void *context;
+    void *socket;
+    int   pkt_size;
+    int   pkt_size_overflow; /*keep track of the largest packet during overflow*/
+} ZMQContext;
+
+#define OFFSET(x) offsetof(ZMQContext, x)
+#define D AV_OPT_FLAG_DECODING_PARAM
+#define E AV_OPT_FLAG_ENCODING_PARAM
+static const AVOption options[] = {
+    { "pkt_size", "Maximum send/read packet size", OFFSET(pkt_size), AV_OPT_TYPE_INT, { .i64 = 32768 }, -1, INT_MAX, .flags = D | E },
+    { NULL }
+};
+
+static int zmq_proto_wait(URLContext *h, void *socket, int write)
+{
+    int ret;
+    int ev = write ? ZMQ_POLLOUT : ZMQ_POLLIN;
+    zmq_pollitem_t items = { .socket = socket, .fd = 0, .events = ev, .revents = 0 };
+    ret = zmq_poll(&items, 1, POLLING_TIME);
+    if (ret == -1) {
+        av_log(h, AV_LOG_ERROR, "Error occured during zmq_poll(): %s\n", ZMQ_STRERROR);
+        return AVERROR_EXTERNAL;
+    }
+    return items.revents & ev ? 0 : AVERROR(EAGAIN);
+}
+
+static int zmq_proto_wait_timeout(URLContext *h, void *socket, int write, int64_t timeout, AVIOInterruptCB *int_cb)
+{
+    int ret;
+    int64_t wait_start = 0;
+
+    while (1) {
+        if (ff_check_interrupt(int_cb))
+            return AVERROR_EXIT;
+        ret = zmq_proto_wait(h, socket, write);
+        if (ret != AVERROR(EAGAIN))
+            return ret;
+        if (timeout > 0) {
+            if (!wait_start)
+                wait_start = av_gettime_relative();
+            else if (av_gettime_relative() - wait_start > timeout)
+                return AVERROR(ETIMEDOUT);
+        }
+    }
+}
+
+static int zmq_proto_open(URLContext *h, const char *uri, int flags)
+{
+    int ret;
+    ZMQContext *s        = h->priv_data;
+    s->pkt_size_overflow = 0;
+    h->is_streamed       = 1;
+
+    if (s->pkt_size > 0)
+        h->max_packet_size = s->pkt_size;
+
+    s->context = zmq_ctx_new();
+    if (!s->context) {
+        /*errno not set on failure during zmq_ctx_new()*/
+        av_log(h, AV_LOG_ERROR, "Error occured during zmq_ctx_new()\n");
+        return AVERROR_EXTERNAL;
+    }
+
+    av_strstart(uri, "zmq:", &uri);
+
+    /*publish during write*/
+    if (h->flags & AVIO_FLAG_WRITE) {
+        s->socket = zmq_socket(s->context, ZMQ_PUB);
+        if (!s->socket) {
+            av_log(h, AV_LOG_ERROR, "Error occured during zmq_socket(): %s\n", ZMQ_STRERROR);
+            zmq_ctx_term(s->context);
+            return AVERROR_EXTERNAL;
+        }
+
+        ret = zmq_bind(s->socket, uri);
+        if (ret == -1) {
+            av_log(h, AV_LOG_ERROR, "Error occured during zmq_bind(): %s\n", ZMQ_STRERROR);
+            zmq_close(s->socket);
+            zmq_ctx_term(s->context);
+            return AVERROR_EXTERNAL;
+        }
+    }
+
+    /*subscribe for read*/
+    if (h->flags & AVIO_FLAG_READ) {
+        s->socket = zmq_socket(s->context, ZMQ_SUB);
+        if (!s->socket) {
+            av_log(h, AV_LOG_ERROR, "Error occured during zmq_socket(): %s\n", ZMQ_STRERROR);
+            zmq_ctx_term(s->context);
+            return AVERROR_EXTERNAL;
+        }
+
+        zmq_setsockopt(s->socket, ZMQ_SUBSCRIBE, "", 0);
+        ret = zmq_connect(s->socket, uri);
+        if (ret == -1) {
+            av_log(h, AV_LOG_ERROR, "Error occured during zmq_connect(): %s\n", ZMQ_STRERROR);
+            zmq_close(s->socket);
+            zmq_ctx_term(s->context);
+            return AVERROR_EXTERNAL;
+        }
+    }
+    return 0;
+}
+
+static int zmq_proto_write(URLContext *h, const unsigned char *buf, int size)
+{
+    int ret;
+    ZMQContext *s = h->priv_data;
+
+    ret = zmq_proto_wait_timeout(h, s->socket, 1, h->rw_timeout, &h->interrupt_callback);
+    if (ret)
+        return ret;
+    ret = zmq_send(s->socket, buf, size, 0);
+    if (ret == -1) {
+        av_log(h, AV_LOG_ERROR, "Error occured during zmq_send(): %s\n", ZMQ_STRERROR);
+        return AVERROR_EXTERNAL;
+    }
+    return ret; /*number of bytes sent*/
+}
+
+static int zmq_proto_read(URLContext *h, unsigned char *buf, int size)
+{
+    int ret;
+    ZMQContext *s = h->priv_data;
+
+    ret = zmq_proto_wait_timeout(h, s->socket, 0, h->rw_timeout, &h->interrupt_callback);
+    if (ret)
+        return ret;
+    ret = zmq_recv(s->socket, buf, size, 0);
+    if (ret == -1) {
+        av_log(h, AV_LOG_ERROR, "Error occured during zmq_recv(): %s\n", ZMQ_STRERROR);
+        return AVERROR_EXTERNAL;
+    }
+    if (ret > size) {
+        s->pkt_size_overflow = FFMAX(s->pkt_size_overflow, ret);
+        av_log(h, AV_LOG_WARNING, "Message exceeds available space in the buffer. Message will be truncated. Setting -pkt_size %d may resolve the issue.\n", s->pkt_size_overflow);
+        ret = size;
+    }
+    return ret; /*number of bytes read*/
+}
+
+static int zmq_proto_close(URLContext *h)
+{
+    ZMQContext *s = h->priv_data;
+    zmq_close(s->socket);
+    zmq_ctx_term(s->context);
+    return 0;
+}
+
+static const AVClass zmq_context_class = {
+    .class_name = "zmq",
+    .item_name  = av_default_item_name,
+    .option     = options,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
+const URLProtocol ff_libzmq_protocol = {
+    .name            = "zmq",
+    .url_close       = zmq_proto_close,
+    .url_open        = zmq_proto_open,
+    .url_read        = zmq_proto_read,
+    .url_write       = zmq_proto_write,
+    .priv_data_size  = sizeof(ZMQContext),
+    .priv_data_class = &zmq_context_class,
+    .flags           = URL_PROTOCOL_FLAG_NETWORK,
+};