From 6fa8edd6b0b13006a2633f98b7fb5735e7fc134d Mon Sep 17 00:00:00 2001
From: Wim Taymans <wtaymans@redhat.com>
Date: Tue, 18 Feb 2014 14:21:20 +0100
Subject: [PATCH] queue2: Fix merging of ranges

Make a method to get the seeking threshold. If data is further away from
this threshold we want to perform a seek upstream.
When the current downloaded range can merge with the next range,
actually include the data of the next range into the current range
instead of discarding it. Also decide if we seek to the write position
of the merged range or continue reading.
---
 plugins/elements/gstqueue2.c | 47 ++++++++++++++++++++++++++++++++------------
 1 file changed, 34 insertions(+), 13 deletions(-)

diff --git a/plugins/elements/gstqueue2.c b/plugins/elements/gstqueue2.c
index f675a45..2a7667a 100644
--- a/plugins/elements/gstqueue2.c
+++ b/plugins/elements/gstqueue2.c
@@ -1065,6 +1065,8 @@ perform_seek_to_offset (GstQueue2 * queue, guint64 offset)
   queue->seeking = TRUE;
   GST_QUEUE2_MUTEX_UNLOCK (queue);
 
+  debug_ranges (queue);
+
   GST_DEBUG_OBJECT (queue, "Seeking to %" G_GUINT64_FORMAT, offset);
 
   event =
@@ -1089,6 +1091,22 @@ perform_seek_to_offset (GstQueue2 * queue, guint64 offset)
   return res;
 }
 
+/* get the threshold for when we decide to seek rather than wait */
+static guint64
+get_seek_threshold (GstQueue2 * queue)
+{
+  guint64 threshold;
+
+  /* FIXME, find a good threshold based on the incoming rate. */
+  threshold = 1024 * 512;
+
+  if (QUEUE_IS_USING_RING_BUFFER (queue)) {
+    threshold = MIN (threshold,
+        QUEUE_MAX_BYTES (queue) - queue->cur_level.bytes);
+  }
+  return threshold;
+}
+
 /* see if there is enough data in the file to read a full buffer */
 static gboolean
 gst_queue2_have_data (GstQueue2 * queue, guint64 offset, guint length)
@@ -1127,13 +1145,8 @@ gst_queue2_have_data (GstQueue2 * queue, guint64 offset, guint length)
         " len %u", offset, length);
     /* we don't have the range, see how far away we are */
     if (!queue->is_eos && queue->current) {
-      /* FIXME, find a good threshold based on the incoming rate. */
-      guint64 threshold = 1024 * 512;
+      guint64 threshold = get_seek_threshold (queue);
 
-      if (QUEUE_IS_USING_RING_BUFFER (queue)) {
-        threshold = MIN (threshold,
-            QUEUE_MAX_BYTES (queue) - queue->cur_level.bytes);
-      }
       if (offset >= queue->current->offset && offset <=
           queue->current->writing_pos + threshold) {
         GST_INFO_OBJECT (queue,
@@ -1615,6 +1628,7 @@ gst_queue2_create_write (GstQueue2 * queue, GstBuffer * buffer)
   guint size, rb_size;
   guint64 writing_pos, new_writing_pos;
   GstQueue2Range *range, *prev, *next;
+  gboolean do_seek = FALSE;
 
   if (QUEUE_IS_USING_RING_BUFFER (queue))
     writing_pos = queue->current->rb_writing_pos;
@@ -1788,15 +1802,19 @@ gst_queue2_create_write (GstQueue2 * queue, GstBuffer * buffer)
           GST_DEBUG_OBJECT (queue, "merging ranges %" G_GUINT64_FORMAT,
               next->writing_pos);
 
-          /* remove the group, we could choose to not read the data in this range
-           * again. This would involve us doing a seek to the current writing position
-           * in the range. FIXME, It would probably make sense to do a seek when there
-           * is a lot of data in the range we merged with to avoid reading it all
-           * again. */
+          /* remove the group */
           queue->current->next = next->next;
-          g_slice_free (GstQueue2Range, next);
 
-          debug_ranges (queue);
+          /* We use the threshold to decide if we want to do a seek or simply
+           * read the data again. If there is not so much data in the range we
+           * prefer to avoid to seek and read it again. */
+          if (next->writing_pos > new_writing_pos + get_seek_threshold (queue)) {
+            /* the new range had more data than the threshold, it's worth keeping
+             * it and doing a seek. */
+            new_writing_pos = next->writing_pos;
+            do_seek = TRUE;
+          }
+          g_slice_free (GstQueue2Range, next);
         }
         goto update_and_signal;
       }
@@ -1846,6 +1864,9 @@ gst_queue2_create_write (GstQueue2 * queue, GstBuffer * buffer)
     } else {
       queue->current->writing_pos = writing_pos = new_writing_pos;
     }
+    if (do_seek)
+      perform_seek_to_offset (queue, new_writing_pos);
+
     update_cur_level (queue, queue->current);
 
     /* update the buffering status */
-- 
2.7.4