unixfd: Serialize buffer metas

Serialize every GstMeta that supports serialization into the NEW_BUFFER
payload. This is especially important for GstVideoMeta in the case of
multiplanar buffers, or if stride!=width.

Sponsored-by: Netflix Inc.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5355>

subprojects/gst-plugins-bad/gst/unixfd/gstunixfd.c

@@ -49,7 +49,7 @@ G_STATIC_ASSERT (sizeof (ReleaseBufferPayload) == 8);
 
 gboolean
 gst_unix_fd_send_command (GSocket * socket, CommandType type, GUnixFDList * fds,
-    const gchar * payload, gsize payload_size, GError ** error)
+    const guint8 * payload, gsize payload_size, GError ** error)
 {
   Command command = { type, payload_size };
   GOutputVector vect[] = {
@@ -76,7 +76,7 @@ gst_unix_fd_send_command (GSocket * socket, CommandType type, GUnixFDList * fds,
 
 gboolean
 gst_unix_fd_receive_command (GSocket * socket, GCancellable * cancellable,
-    CommandType * type, GUnixFDList ** fds, gchar ** payload,
+    CommandType * type, GUnixFDList ** fds, guint8 ** payload,
     gsize * payload_size, GError ** error)
 {
   Command command;
@@ -98,8 +98,8 @@ gst_unix_fd_receive_command (GSocket * socket, GCancellable * cancellable,
   if (command.payload_size > 0) {
     *payload = g_malloc (command.payload_size);
     *payload_size = command.payload_size;
-    if (g_socket_receive (socket, *payload, command.payload_size, cancellable,
-            error) < (gssize) command.payload_size) {
+    if (g_socket_receive (socket, (gchar *) * payload, command.payload_size,
+            cancellable, error) < (gssize) command.payload_size) {
       g_clear_pointer (payload, g_free);
       ret = FALSE;
       goto out;
@@ -133,8 +133,8 @@ out:
 }
 
 gboolean
-gst_unix_fd_parse_new_buffer (gchar * payload, gsize payload_size,
-    NewBufferPayload ** new_buffer)
+gst_unix_fd_parse_new_buffer (guint8 * payload, gsize payload_size,
+    NewBufferPayload ** new_buffer, guint32 * consumed)
 {
   if (payload == NULL || payload_size < sizeof (NewBufferPayload))
     return FALSE;
@@ -146,11 +146,13 @@ gst_unix_fd_parse_new_buffer (gchar * payload, gsize payload_size,
   if (payload_size < struct_size)
     return FALSE;
 
+  *consumed = struct_size;
+
   return TRUE;
 }
 
 gboolean
-gst_unix_fd_parse_release_buffer (gchar * payload, gsize payload_size,
+gst_unix_fd_parse_release_buffer (guint8 * payload, gsize payload_size,
     ReleaseBufferPayload ** release_buffer)
 {
   if (payload == NULL || payload_size < sizeof (ReleaseBufferPayload))
@@ -162,12 +164,12 @@ gst_unix_fd_parse_release_buffer (gchar * payload, gsize payload_size,
 }
 
 gboolean
-gst_unix_fd_parse_caps (gchar * payload, gsize payload_size, gchar ** caps_str)
+gst_unix_fd_parse_caps (guint8 * payload, gsize payload_size, gchar ** caps_str)
 {
   if (payload == NULL || payload_size < 1 || payload[payload_size - 1] != '\0')
     return FALSE;
 
-  *caps_str = payload;
+  *caps_str = (gchar *) payload;
 
   return TRUE;
 }

subprojects/gst-plugins-bad/gst/unixfd/gstunixfd.h

@@ -57,7 +57,7 @@ typedef struct {
   guint32 flags;
   guint8 type;
   guint8 n_memory;
-  guint16 padding;
+  guint16 n_meta;
   MemoryPayload memories[];
 } NewBufferPayload;
 
@@ -66,17 +66,17 @@ typedef struct {
 } ReleaseBufferPayload;
 
 gboolean gst_unix_fd_send_command(GSocket * socket, CommandType type,
-    GUnixFDList * fds, const gchar * payload, gsize payload_size,
+    GUnixFDList * fds, const guint8 * payload, gsize payload_size,
     GError ** error);
-gboolean gst_unix_fd_receive_command(GSocket * socket,
-    GCancellable * cancellable, CommandType *type, GUnixFDList ** fds,
-    gchar ** payload, gsize *payload_size, GError ** error);
+gboolean gst_unix_fd_receive_command (GSocket *socket,
+    GCancellable *cancellable, CommandType *type, GUnixFDList **fds,
+    guint8 **payload, gsize *payload_size, GError **error);
 
-gboolean gst_unix_fd_parse_new_buffer(gchar *payload, gsize payload_size,
-    NewBufferPayload **new_buffer);
-gboolean gst_unix_fd_parse_release_buffer(gchar *payload, gsize payload_size,
+gboolean gst_unix_fd_parse_new_buffer (guint8 *payload, gsize payload_size,
+    NewBufferPayload **new_buffer, guint32 *consumed);
+gboolean gst_unix_fd_parse_release_buffer(guint8 *payload, gsize payload_size,
     ReleaseBufferPayload **release_buffer);
-gboolean gst_unix_fd_parse_caps(gchar *payload, gsize payload_size,
+gboolean gst_unix_fd_parse_caps (guint8 *payload, gsize payload_size,
     gchar **caps_str);
 
 GSocket *gst_unix_fd_socket_new(const gchar *socket_path,

subprojects/gst-plugins-bad/gst/unixfd/gstunixfdsink.c

@@ -86,6 +86,7 @@ struct _GstUnixFdSink
   GHashTable *clients;
   GstCaps *caps;
   gboolean uses_monotonic_clock;
+  GByteArray *payload;
 };
 
 G_DEFINE_TYPE (GstUnixFdSink, gst_unix_fd_sink, GST_TYPE_BASE_SINK);
@@ -199,7 +200,7 @@ incoming_command_cb (GSocket * socket, GIOCondition cond, gpointer user_data)
   GstUnixFdSink *self = user_data;
   Client *client;
   CommandType command;
-  gchar *payload = NULL;
+  guint8 *payload = NULL;
   gsize payload_size;
   GError *error = NULL;
 
@@ -264,12 +265,12 @@ on_error:
   return G_SOURCE_REMOVE;
 }
 
-static gchar *
+static guint8 *
 caps_to_payload (GstCaps * caps, gsize * payload_size)
 {
   gchar *payload = gst_caps_to_string (caps);
   *payload_size = strlen (payload) + 1;
-  return payload;
+  return (guint8 *) payload;
 }
 
 static gboolean
@@ -303,7 +304,7 @@ new_client_cb (GSocket * socket, GIOCondition cond, gpointer user_data)
    * we don't want this client to miss a caps event or receive a buffer while we
    * send initial caps. */
   gsize payload_size;
-  gchar *payload = caps_to_payload (self->caps, &payload_size);
+  guint8 *payload = caps_to_payload (self->caps, &payload_size);
   if (!gst_unix_fd_send_command (client_socket, COMMAND_TYPE_CAPS, NULL,
           payload, payload_size, &error)) {
     GST_ERROR_OBJECT (self, "Failed to send caps to new client %p: %s", client,
@@ -365,6 +366,13 @@ gst_unix_fd_sink_start (GstBaseSink * bsink)
 
   self->thread = g_thread_new ("unixfdsink", thread_cb, self);
 
+  /* Preallocate the minimum payload size for a buffer with a single memory and
+   * no metas. Chances are that every buffer will require roughly the same
+   * payload size, by reusing the same GByteArray we avoid reallocations. */
+  self->payload =
+      g_byte_array_sized_new (sizeof (NewBufferPayload) +
+      sizeof (MemoryPayload));
+
 out:
   GST_OBJECT_UNLOCK (self);
   g_clear_error (&error);
@@ -385,6 +393,7 @@ gst_unix_fd_sink_stop (GstBaseSink * bsink)
   g_clear_object (&self->socket);
   gst_clear_caps (&self->caps);
   g_hash_table_remove_all (self->clients);
+  g_clear_pointer (&self->payload, g_byte_array_unref);
 
   if (self->socket_type == G_UNIX_SOCKET_ADDRESS_PATH)
     g_unlink (self->socket_path);
@@ -394,7 +403,7 @@ gst_unix_fd_sink_stop (GstBaseSink * bsink)
 
 static void
 send_command_to_all (GstUnixFdSink * self, CommandType type, GUnixFDList * fds,
-    const gchar * payload, gsize payload_size, GstBuffer * buffer)
+    const guint8 * payload, gsize payload_size, GstBuffer * buffer)
 {
   GHashTableIter iter;
   GSocket *socket;
@@ -435,6 +444,21 @@ calculate_timestamp (GstClockTime timestamp, GstClockTime base_time,
   return timestamp;
 }
 
+static guint16
+serialize_metas (GstBuffer * buffer, GByteArray * payload)
+{
+  gpointer state = NULL;
+  GstMeta *meta;
+  guint16 n_meta = 0;
+
+  while ((meta = gst_buffer_iterate_meta (buffer, &state)) != NULL) {
+    if (gst_meta_serialize_simple (meta, payload))
+      n_meta++;
+  }
+
+  return n_meta;
+}
+
 static GstFlowReturn
 gst_unix_fd_sink_render (GstBaseSink * bsink, GstBuffer * buffer)
 {
@@ -442,11 +466,11 @@ gst_unix_fd_sink_render (GstBaseSink * bsink, GstBuffer * buffer)
   GstFlowReturn ret = GST_FLOW_OK;
   GError *error = NULL;
 
-  /* Allocate payload */
   guint n_memory = gst_buffer_n_memory (buffer);
-  gsize payload_size =
+  gsize struct_size =
       sizeof (NewBufferPayload) + sizeof (MemoryPayload) * n_memory;
-  gchar *payload = g_malloc0 (payload_size);
+  g_byte_array_set_size (self->payload, struct_size);
+  guint32 n_meta = serialize_metas (buffer, self->payload);
 
   GstClockTime latency = gst_base_sink_get_latency (GST_BASE_SINK_CAST (self));
   GstClockTime base_time = gst_element_get_base_time (GST_ELEMENT_CAST (self));
@@ -456,7 +480,7 @@ gst_unix_fd_sink_render (GstBaseSink * bsink, GstBuffer * buffer)
         gst_clock_get_time (GST_ELEMENT_CLOCK (self)));
   }
 
-  NewBufferPayload *new_buffer = (NewBufferPayload *) payload;
+  NewBufferPayload *new_buffer = (NewBufferPayload *) self->payload->data;
   /* Cast buffer pointer to guint64 identifier. Client will send us back that
    * id so we know which buffer to unref. */
   new_buffer->id = (guint64) buffer;
@@ -472,6 +496,7 @@ gst_unix_fd_sink_render (GstBaseSink * bsink, GstBuffer * buffer)
   new_buffer->flags = GST_BUFFER_FLAGS (buffer);
   new_buffer->type = MEMORY_TYPE_DEFAULT;
   new_buffer->n_memory = n_memory;
+  new_buffer->n_meta = n_meta;
 
   gboolean dmabuf_count = 0;
   GUnixFDList *fds = g_unix_fd_list_new ();
@@ -507,14 +532,13 @@ gst_unix_fd_sink_render (GstBaseSink * bsink, GstBuffer * buffer)
     new_buffer->type = MEMORY_TYPE_DMABUF;
 
   GST_OBJECT_LOCK (self);
-  send_command_to_all (self, COMMAND_TYPE_NEW_BUFFER, fds, payload,
-      payload_size, buffer);
+  send_command_to_all (self, COMMAND_TYPE_NEW_BUFFER, fds,
+      self->payload->data, self->payload->len, buffer);
   GST_OBJECT_UNLOCK (self);
 
 out:
   g_clear_object (&fds);
   g_clear_error (&error);
-  g_free (payload);
   return ret;
 }
 
@@ -532,7 +556,7 @@ gst_unix_fd_sink_event (GstBaseSink * bsink, GstEvent * event)
       GST_DEBUG_OBJECT (self, "Send new caps to all clients: %" GST_PTR_FORMAT,
           self->caps);
       gsize payload_size;
-      gchar *payload = caps_to_payload (self->caps, &payload_size);
+      guint8 *payload = caps_to_payload (self->caps, &payload_size);
       send_command_to_all (self, COMMAND_TYPE_CAPS, NULL, payload, payload_size,
           NULL);
       g_free (payload);

subprojects/gst-plugins-bad/gst/unixfd/gstunixfdsrc.c

@@ -103,7 +103,7 @@ memory_weak_ref_cb (GstUnixFdSrc * self, GstMemory * mem)
     ReleaseBufferPayload payload = { ctx->id };
     GError *error = NULL;
     if (!gst_unix_fd_send_command (self->socket, COMMAND_TYPE_RELEASE_BUFFER,
-            NULL, (const gchar *) &payload, sizeof (payload), &error)) {
+            NULL, (guint8 *) & payload, sizeof (payload), &error)) {
       GST_WARNING_OBJECT (self, "Failed to send release-buffer command: %s",
           error->message);
       g_clear_error (&error);
@@ -301,7 +301,7 @@ gst_unix_fd_src_create (GstPushSrc * psrc, GstBuffer ** outbuf)
   GstUnixFdSrc *self = GST_UNIX_FD_SRC (psrc);
   CommandType command;
   GUnixFDList *fds = NULL;
-  gchar *payload = NULL;
+  guint8 *payload = NULL;
   gsize payload_size;
   GError *error = NULL;
   GstFlowReturn ret = GST_FLOW_OK;
@@ -327,7 +327,9 @@ again:
       goto on_error;
     case COMMAND_TYPE_NEW_BUFFER:{
       NewBufferPayload *new_buffer;
-      if (!gst_unix_fd_parse_new_buffer (payload, payload_size, &new_buffer)) {
+      guint32 payload_off = 0;
+      if (!gst_unix_fd_parse_new_buffer (payload, payload_size, &new_buffer,
+              &payload_off)) {
         GST_ERROR_OBJECT (self, "Received new-buffer with wrong payload size");
         ret = GST_FLOW_ERROR;
         goto on_error;
@@ -341,8 +343,8 @@ again:
 
       if (g_unix_fd_list_get_length (fds) != new_buffer->n_memory) {
         GST_ERROR_OBJECT (self,
-            "Received new buffer command with %d file descriptors instead of %d",
-            g_unix_fd_list_get_length (fds), new_buffer->n_memory);
+            "Received new buffer command with %d file descriptors instead of "
+            "%d", g_unix_fd_list_get_length (fds), new_buffer->n_memory);
         ret = GST_FLOW_ERROR;
         goto on_error;
       }
@@ -379,6 +381,18 @@ again:
       GST_BUFFER_OFFSET_END (*outbuf) = new_buffer->offset_end;
       GST_BUFFER_FLAGS (*outbuf) = new_buffer->flags;
 
+      for (int i = 0; i < new_buffer->n_meta; i++) {
+        guint32 consumed = 0;
+        gst_meta_deserialize (*outbuf, (guint8 *) payload + payload_off,
+            payload_size - payload_off, &consumed);
+        if (consumed == 0) {
+          GST_ERROR_OBJECT (self, "Malformed meta serialization");
+          ret = GST_FLOW_ERROR;
+          goto on_error;
+        }
+        payload_off += consumed;
+      }
+
       GST_OBJECT_LOCK (self);
       for (int i = 0; i < new_buffer->n_memory; i++) {
         GstMemory *mem = gst_fd_allocator_alloc (allocator, fds_arr[i],

subprojects/gst-plugins-bad/tests/check/elements/unixfd.c

@@ -37,10 +37,26 @@ wait_preroll (GstElement * element)
   fail_unless (state_res == GST_STATE_CHANGE_SUCCESS);
 }
 
+static GstPadProbeReturn
+buffer_pad_probe_cb (GstPad * pad, GstPadProbeInfo * info, gpointer user_data)
+{
+  GstBuffer *buffer = GST_PAD_PROBE_INFO_BUFFER (info);
+  if (buffer != NULL) {
+    GstCustomMeta *cmeta =
+        gst_buffer_add_custom_meta (buffer, "unix-fd-custom-meta");
+    GstStructure *s = gst_custom_meta_get_structure (cmeta);
+    gst_structure_set (s, "field", G_TYPE_INT, 42, NULL);
+  }
+  return GST_PAD_PROBE_OK;
+}
+
 GST_START_TEST (test_unixfd_videotestsrc)
 {
   GError *error = NULL;
 
+  const gchar *tags[] = { NULL };
+  gst_meta_register_custom ("unix-fd-custom-meta", tags, NULL, NULL, NULL);
+
   /* Ensure we don't have socket from previous failed test */
   gchar *socket_path =
       g_strdup_printf ("%s/unixfd-test-socket", g_get_user_runtime_dir ());
@@ -50,15 +66,26 @@ GST_START_TEST (test_unixfd_videotestsrc)
 
   /* Setup source */
   gchar *pipeline_str =
-      g_strdup_printf ("videotestsrc ! unixfdsink socket-path=%s", socket_path);
+      g_strdup_printf ("videotestsrc name=src ! unixfdsink socket-path=%s",
+      socket_path);
   GstElement *pipeline_service = gst_parse_launch (pipeline_str, &error);
   g_assert_no_error (error);
   g_free (pipeline_str);
+
+  /* Add a custom meta on each buffer */
+  GstElement *src = gst_bin_get_by_name (GST_BIN (pipeline_service), "src");
+  GstPad *pad = gst_element_get_static_pad (src, "src");
+  gst_pad_add_probe (pad, GST_PAD_PROBE_TYPE_BUFFER, buffer_pad_probe_cb, NULL,
+      NULL);
+  gst_object_unref (src);
+  gst_object_unref (pad);
+
   wait_preroll (pipeline_service);
 
   /* Setup sink */
   pipeline_str =
-      g_strdup_printf ("unixfdsrc socket-path=%s ! fakesink", socket_path);
+      g_strdup_printf ("unixfdsrc socket-path=%s ! fakesink name=sink",
+      socket_path);
   GstElement *pipeline_client_1 = gst_parse_launch (pipeline_str, &error);
   g_assert_no_error (error);
   wait_preroll (pipeline_client_1);
@@ -73,6 +100,22 @@ GST_START_TEST (test_unixfd_videotestsrc)
   g_assert_no_error (error);
   wait_preroll (pipeline_client_2);
 
+  /* Check we received our custom meta */
+  GstSample *sample;
+  GstElement *sink = gst_bin_get_by_name (GST_BIN (pipeline_client_2), "sink");
+  g_object_get (sink, "last-sample", &sample, NULL);
+  fail_unless (sample);
+  GstBuffer *buffer = gst_sample_get_buffer (sample);
+  GstCustomMeta *cmeta =
+      gst_buffer_get_custom_meta (buffer, "unix-fd-custom-meta");
+  fail_unless (cmeta);
+  GstStructure *s = gst_custom_meta_get_structure (cmeta);
+  gint value;
+  fail_unless (gst_structure_get_int (s, "field", &value));
+  fail_unless_equals_int (value, 42);
+  gst_object_unref (sink);
+  gst_sample_unref (sample);
+
   /* Teardown */
   fail_unless (gst_element_set_state (pipeline_client_1,
           GST_STATE_NULL) == GST_STATE_CHANGE_SUCCESS);