asfmux: handle streams with different start times

Prevents losing sync when remuxing streams with different
start times. The smallest start time is selected as
the base time and all timestamps are subtracted
from it to get the actual time to be used when
muxing and building indexes

Fixes #586848

2 files changed, 26 insertions, 1 deletions

diff --git a/gst/asfmux/gstasfmux.c b/gst/asfmux/gstasfmux.c
index 4d4fa2e5a..3afc936c9 100644
--- a/gst/asfmux/gstasfmux.c
+++ b/gst/asfmux/gstasfmux.c
@@ -216,6 +216,7 @@ gst_asf_mux_reset (GstAsfMux * asfmux)
   asfmux->total_data_packets = 0;
   asfmux->file_size = 0;
   asfmux->packet_size = 0;
+  asfmux->first_ts = GST_CLOCK_TIME_NONE;
 
   if (asfmux->payloads) {
     GSList *walk;
@@ -1763,8 +1764,12 @@ gst_asf_mux_process_buffer (GstAsfMux * asfmux, GstAsfPad * pad,
     gst_asf_payload_free (payload);
     return GST_FLOW_ERROR;
   }
+
+  g_assert (GST_CLOCK_TIME_IS_VALID (asfmux->first_ts));
+  g_assert (GST_CLOCK_TIME_IS_VALID (pad->first_ts));
+
   payload->presentation_time = asfmux->preroll +
-      (GST_BUFFER_TIMESTAMP (buf) / GST_MSECOND);
+      ((GST_BUFFER_TIMESTAMP (buf) - asfmux->first_ts) / GST_MSECOND);
 
   /* update counting values */
   pad->media_object_number = (pad->media_object_number + 1) % 256;
@@ -1833,6 +1838,21 @@ gst_asf_mux_collected (GstCollectPads * collect, gpointer data)
       continue;
     }
     time = GST_BUFFER_TIMESTAMP (buf);
+
+    /* check the ts for getting the first time */
+    if (!GST_CLOCK_TIME_IS_VALID (pad->first_ts) &&
+        GST_CLOCK_TIME_IS_VALID (time)) {
+      GST_DEBUG_OBJECT (asfmux, "First ts for stream number %" G_GUINT16_FORMAT
+          ": %" GST_TIME_FORMAT, pad->stream_number, GST_TIME_ARGS (time));
+      pad->first_ts = time;
+      if (!GST_CLOCK_TIME_IS_VALID (asfmux->first_ts) ||
+          time < asfmux->first_ts) {
+        GST_DEBUG_OBJECT (asfmux, "New first ts for file %" GST_TIME_FORMAT,
+            GST_TIME_ARGS (time));
+        asfmux->first_ts = time;
+      }
+    }
+
     gst_buffer_unref (buf);
 
     if (best_pad == NULL || !GST_CLOCK_TIME_IS_VALID (time) ||
@@ -1887,6 +1907,8 @@ gst_asf_mux_pad_reset (GstAsfPad * pad)
     gst_tag_list_free (pad->taglist);
   pad->taglist = NULL;
 
+  pad->first_ts = GST_CLOCK_TIME_NONE;
+
   if (pad->is_audio) {
     GstAsfAudioPad *audiopad = (GstAsfAudioPad *) pad;
     audiopad->audioinfo.rate = 0;
diff --git a/gst/asfmux/gstasfmux.h b/gst/asfmux/gstasfmux.h
index 4e13b36a6..015c8b9ab 100644
--- a/gst/asfmux/gstasfmux.h
+++ b/gst/asfmux/gstasfmux.h
@@ -65,6 +65,7 @@ struct _GstAsfPad
   guint32 bitrate;
 
   GstClockTime play_duration;
+  GstClockTime first_ts;
 
   GstBuffer *codec_data;
 
@@ -136,6 +137,8 @@ struct _GstAsfMux
   guint64 preroll;              /* milisecs */
   gboolean merge_stream_tags;
 
+  GstClockTime first_ts;
+
   /* pads */
   GstPad *srcpad;