asfdemux: Make sure we don't end up with negative timestamps.

Some files have payload with timestamps smaller than the preroll duration.
Instead of blindly substracting the preroll value (and ending up with
insanely high timestamps on the outgoing buffers), we make sure we
never go below 0.

Fixes #610432

diff --git a/gst/asfdemux/asfpacket.c b/gst/asfdemux/asfpacket.c
index 1c0ecb0..d266593 100644 (file)
--- a/gst/asfdemux/asfpacket.c
+++ b/gst/asfdemux/asfpacket.c
@@ -357,7 +357,10 @@ gst_asf_demux_parse_payload (GstASFDemux * demux, AsfPacket * packet,
     if (payload.rep_data_len >= 8) {
       payload.mo_size = GST_READ_UINT32_LE (payload.rep_data);
       payload.ts = GST_READ_UINT32_LE (payload.rep_data + 4) * GST_MSECOND;
-      payload.ts -= demux->preroll;
+      if (G_UNLIKELY (payload.ts < demux->preroll))
+        payload.ts = 0;
+      else
+        payload.ts -= demux->preroll;
       asf_payload_parse_replicated_data_extensions (stream, &payload);
 
       GST_LOG_OBJECT (demux, "media object size   : %u", payload.mo_size);
@@ -412,7 +415,11 @@ gst_asf_demux_parse_payload (GstASFDemux * demux, AsfPacket * packet,
     *p_data += payload_len;
     *p_size -= payload_len;
 
-    ts = payload.mo_offset * GST_MSECOND - demux->preroll;
+    ts = payload.mo_offset * GST_MSECOND;
+    if (G_UNLIKELY (ts < demux->preroll))
+      ts = 0;
+    else
+      ts -= demux->preroll;
     ts_delta = payload.rep_data[0] * GST_MSECOND;
 
     for (num = 0; payload_len > 0; ++num) {