From f062b780518dcb7628dabd66f4764ef9ca06f1fb Mon Sep 17 00:00:00 2001
From: Edward Hervey <bilboed@bilboed.com>
Date: Fri, 18 Apr 2014 16:23:43 +0200
Subject: [PATCH] mpegtspacketizer: Improve ts_to_offset code

* Search in current pending values first. For CBR streams we can very
  easily end up having just one initial observations and then nothing
  else (since the bitrate doesn't change).
* Use one group whether we are in that group *OR* if there is only
  one group.
* If the group to use isn't closed (points are being accumulated in the
  PCROffsetCurrent), use the latest data available for calculation
* If in the unlikelyness that all of this *still* didn't produce more
  than one data point, just return the initial offset
---
 gst/mpegtsdemux/mpegtspacketizer.c | 45 ++++++++++++++++++++++--------
 1 file changed, 34 insertions(+), 11 deletions(-)

diff --git a/gst/mpegtsdemux/mpegtspacketizer.c b/gst/mpegtsdemux/mpegtspacketizer.c
index 088028ce9c..8880905d37 100644
--- a/gst/mpegtsdemux/mpegtspacketizer.c
+++ b/gst/mpegtsdemux/mpegtspacketizer.c
@@ -2211,6 +2211,7 @@ mpegts_packetizer_ts_to_offset (MpegTSPacketizer2 * packetizer,
   guint64 res;
   PCROffsetGroup *nextgroup = NULL, *prevgroup = NULL;
   guint64 querypcr, firstpcr, lastpcr, firstoffset, lastoffset;
+  PCROffsetCurrent *current;
   GList *tmp;
 
   if (!packetizer->calculate_offset)
@@ -2225,6 +2226,16 @@ mpegts_packetizer_ts_to_offset (MpegTSPacketizer2 * packetizer,
 
   GST_DEBUG ("Searching offset for ts %" GST_TIME_FORMAT, GST_TIME_ARGS (ts));
 
+  /* First check if we're within the current pending group */
+  current = pcrtable->current;
+  if (current && current->group && (querypcr >= current->group->pcr_offset) &&
+      querypcr - current->group->pcr_offset <=
+      current->pending[current->last].pcr) {
+    GST_DEBUG ("pcr is in current group");
+    nextgroup = current->group;
+    goto calculate_points;
+  }
+
   /* Find the neighbouring groups */
   for (tmp = pcrtable->groups; tmp; tmp = tmp->next) {
     nextgroup = (PCROffsetGroup *) tmp->data;
@@ -2256,15 +2267,25 @@ mpegts_packetizer_ts_to_offset (MpegTSPacketizer2 * packetizer,
     }
   }
 
-  if (nextgroup == prevgroup) {
-    GST_DEBUG ("In group");
-    firstoffset = prevgroup->first_offset;
-    firstpcr = prevgroup->pcr_offset;
-    lastoffset =
-        prevgroup->values[prevgroup->last_value].offset +
-        prevgroup->first_offset;
-    lastpcr =
-        prevgroup->values[prevgroup->last_value].pcr + prevgroup->pcr_offset;
+calculate_points:
+
+  GST_DEBUG ("nextgroup:%p, prevgroup:%p", nextgroup, prevgroup);
+
+  if (nextgroup == prevgroup || prevgroup == NULL) {
+    /* We use the current group to calculate position:
+     * * if the PCR is within this group
+     * * if there is only one group to use for calculation
+     */
+    GST_DEBUG ("In group or after last one");
+    lastoffset = firstoffset = nextgroup->first_offset;
+    lastpcr = firstpcr = nextgroup->pcr_offset;
+    if (current && nextgroup == current->group) {
+      lastoffset += current->pending[current->last].offset;
+      lastpcr += current->pending[current->last].pcr;
+    } else {
+      lastoffset += nextgroup->values[nextgroup->last_value].offset;
+      lastpcr += nextgroup->values[nextgroup->last_value].pcr;
+    }
   } else if (prevgroup) {
     GST_DEBUG ("Between group");
     lastoffset = nextgroup->first_offset;
@@ -2284,8 +2305,10 @@ mpegts_packetizer_ts_to_offset (MpegTSPacketizer2 * packetizer,
   GST_DEBUG ("Using last PCR %" G_GUINT64_FORMAT " offset %" G_GUINT64_FORMAT,
       lastpcr, lastoffset);
 
-  res = firstoffset + gst_util_uint64_scale (querypcr - firstpcr,
-      lastoffset - firstoffset, lastpcr - firstpcr);
+  res = firstoffset;
+  if (lastpcr != firstpcr)
+    res += gst_util_uint64_scale (querypcr - firstpcr,
+        lastoffset - firstoffset, lastpcr - firstpcr);
 
   GST_DEBUG ("Returning offset %" G_GUINT64_FORMAT " for ts %"
       GST_TIME_FORMAT, res, GST_TIME_ARGS (ts));