From a6552ee02ef441e239b9c317914a150d499fea3e Mon Sep 17 00:00:00 2001
From: Wim Taymans <wtaymans@redhat.com>
Date: Fri, 11 Jan 2019 16:37:40 +0100
Subject: [PATCH] video-converter: fix number of allocated lines

We make an allocator for temporary lines and then use this for all
the steps in the conversion that can do in-place processing.

Keep track of the number of lines each step needs and use this to
allocate the right number of lines.

Previously we would not always allocate enough lines and we would
end up with conversion errors as lines would be reused prematurely.

Fixes #350
---
 gst-libs/gst/video/video-converter.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/gst-libs/gst/video/video-converter.c b/gst-libs/gst/video/video-converter.c
index 4faf75078e..5935f126c9 100644
--- a/gst-libs/gst/video/video-converter.c
+++ b/gst-libs/gst/video/video-converter.c
@@ -2070,20 +2070,18 @@ chain_pack (GstVideoConverter * convert, GstLineCache * prev, gint idx)
 static void
 setup_allocators (GstVideoConverter * convert)
 {
-  GstLineCache *cache;
+  GstLineCache *cache, *prev;
   GstLineCacheAllocLineFunc alloc_line;
   gboolean alloc_writable;
   gpointer user_data;
   GDestroyNotify notify;
-  gint width, n_lines;
+  gint width;
   gint i;
 
   width = MAX (convert->in_maxwidth, convert->out_maxwidth);
   width += convert->out_x;
 
   for (i = 0; i < convert->conversion_runner->n_threads; i++) {
-    n_lines = 1;
-
     /* start with using dest lines if we can directly write into it */
     if (convert->identity_pack) {
       alloc_line = get_dest_line;
@@ -2101,12 +2099,24 @@ setup_allocators (GstVideoConverter * convert)
       alloc_writable = convert->borderline != NULL;
     }
 
+    /* First step, try to calculate how many temp lines we need. Go backwards,
+     * keep track of the maximum number of lines we need for each intermediate
+     * step.  */
+    for (prev = cache = convert->pack_lines[i]; cache; cache = cache->prev) {
+      GST_DEBUG ("looking at cache %p, %d lines, %d backlog", cache,
+          cache->n_lines, cache->backlog);
+      prev->n_lines = MAX (prev->n_lines, cache->n_lines);
+      if (!cache->pass_alloc) {
+        GST_DEBUG ("cache %p, needs %d lines", prev, prev->n_lines);
+        prev = cache;
+      }
+    }
+
     /* now walk backwards, we try to write into the dest lines directly
      * and keep track if the source needs to be writable */
     for (cache = convert->pack_lines[i]; cache; cache = cache->prev) {
       gst_line_cache_set_alloc_line_func (cache, alloc_line, user_data, notify);
       cache->alloc_writable = alloc_writable;
-      n_lines = MAX (n_lines, cache->n_lines);
 
       /* make sure only one cache frees the allocator */
       notify = NULL;
@@ -2115,11 +2125,10 @@ setup_allocators (GstVideoConverter * convert)
         /* can't pass allocator, make new temp line allocator */
         user_data =
             converter_alloc_new (sizeof (guint16) * width * 4,
-            n_lines + cache->backlog, convert, NULL);
+            cache->n_lines + cache->backlog, convert, NULL);
         notify = (GDestroyNotify) converter_alloc_free;
         alloc_line = get_temp_line;
         alloc_writable = FALSE;
-        n_lines = cache->n_lines;
       }
       /* if someone writes to the input, we need a writable line from the
        * previous cache */