From 1cd0dd3503c141954ba0740cc5eca6676af9c028 Mon Sep 17 00:00:00 2001
From: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Date: Tue, 5 Sep 2017 15:57:51 -0400
Subject: [PATCH] tee: Allocate one more buffer when multi-plexing

This extra buffer ensure that the downstream threads are not starved
when multiplexing a stream.

https://bugzilla.gnome.org/show_bug.cgi?id=730758
---
 plugins/elements/gsttee.c  | 8 ++++++++
 tests/check/elements/tee.c | 3 ++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/plugins/elements/gsttee.c b/plugins/elements/gsttee.c
index ce5449a34c..bc38b6b4ba 100644
--- a/plugins/elements/gsttee.c
+++ b/plugins/elements/gsttee.c
@@ -573,6 +573,7 @@ struct AllocQueryCtx
   guint size;
   guint min_buffers;
   gboolean first_query;
+  guint num_pads;
 };
 
 /* This function will aggregate some of the allocation query information with
@@ -715,6 +716,7 @@ gst_tee_query_allocation (const GValue * item, GValue * ret, gpointer user_data)
   }
 
   ctx->first_query = FALSE;
+  ctx->num_pads++;
   gst_query_unref (query);
 
   return TRUE;
@@ -758,6 +760,7 @@ gst_tee_sink_query (GstPad * pad, GstObject * parent, GstQuery * query)
         gst_allocation_params_init (&ctx.params);
         ctx.size = 0;
         ctx.min_buffers = 0;
+        ctx.num_pads = 0;
         gst_tee_clear_query_allocation_meta (query);
       }
 
@@ -789,6 +792,11 @@ gst_tee_sink_query (GstPad * pad, GstObject * parent, GstQuery * query)
         }
 #endif
 
+        /* Allocate one more buffers when multiplexing so we don't starve the
+         * downstream threads. */
+        if (ctx.num_pads > 1)
+          ctx.min_buffers++;
+
         gst_query_add_allocation_param (ctx.query, NULL, &ctx.params);
         gst_query_add_allocation_pool (ctx.query, NULL, ctx.size,
             ctx.min_buffers, 0);
diff --git a/tests/check/elements/tee.c b/tests/check/elements/tee.c
index 5f4c900090..de63c1fd1e 100644
--- a/tests/check/elements/tee.c
+++ b/tests/check/elements/tee.c
@@ -802,7 +802,8 @@ GST_START_TEST (test_allocation_query)
   fail_unless (gst_query_get_n_allocation_pools (query), 1);
   gst_query_parse_nth_allocation_pool (query, 0, NULL, &size, &min, &max);
   fail_unless (size == 130);
-  fail_unless (min == 2);
+  /* The tee will allocate one more buffer when multiplexing */
+  fail_unless (min == 2 + 1);
   fail_unless (max == 0);
 
   fail_unless (gst_query_get_n_allocation_params (query), 1);