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qtdemux: When using a buffered mdat, store all received data for later use

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In push mode, when qtdemux can't use a seek to skip the mdat buffer it has
to buffer it for later use.

The issue is that after parsing the next moov/moof, there might be some
trailing bytes from the next atom in the file. This data was being discarded
along with the already parsed moov/moof and playback would fail to continue
after the contents of this moov/moof are played.

This is particularly bad on fragmented files that have the mdat before the
corresponding moof. So you'd get:

mdat|moof|mdat|moof ...

When a moof was received, it usually came with some extra bytes that would
belong to the next mdat (because upstream doesn't care about atoms alignment).
So those bytes were being discarded and playback would fail.

This patch makes qtdemux store those extra bytes to reuse them later after the
mdat is emptied.

https://bugzilla.gnome.org/show_bug.cgi?id=710623
This commit is contained in:
Thiago Santos 2013-10-25 11:42:37 -03:00
parent fd89e36c8a
commit 0e78ffc9d6
2 changed files with 42 additions and 1 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

34
gst/isomp4/qtdemux.c
View file

@ -532,6 +532,8 @@ gst_qtdemux_init (GstQTDemux * qtdemux)
qtdemux->got_moov = FALSE;
qtdemux->mdatoffset = GST_CLOCK_TIME_NONE;
qtdemux->mdatbuffer = NULL;
qtdemux->restoredata_buffer = NULL;
qtdemux->restoredata_offset = GST_CLOCK_TIME_NONE;
qtdemux->fragment_start = -1;
qtdemux->media_caps = NULL;
qtdemux->exposed = FALSE;
@ -1804,9 +1806,13 @@ gst_qtdemux_reset (GstQTDemux * qtdemux, gboolean hard)
qtdemux->first_mdat = -1;
qtdemux->header_size = 0;
qtdemux->mdatoffset = GST_CLOCK_TIME_NONE;
qtdemux->restoredata_offset = GST_CLOCK_TIME_NONE;
if (qtdemux->mdatbuffer)
gst_buffer_unref (qtdemux->mdatbuffer);
if (qtdemux->restoredata_buffer)
gst_buffer_unref (qtdemux->restoredata_buffer);
qtdemux->mdatbuffer = NULL;
qtdemux->restoredata_buffer = NULL;
qtdemux->mdatleft = 0;
if (qtdemux->comp_brands)
gst_buffer_unref (qtdemux->comp_brands);
@ -4770,13 +4776,29 @@ gst_qtdemux_chain (GstPad * sinkpad, GstObject * parent, GstBuffer * inbuf)
data = NULL;
if (demux->mdatbuffer && demux->n_streams) {
gsize remaining_data_size = 0;
/* the mdat was before the header */
GST_DEBUG_OBJECT (demux, "We have n_streams:%d and mdatbuffer:%p",
demux->n_streams, demux->mdatbuffer);
/* restore our adapter/offset view of things with upstream;
* put preceding buffered data ahead of current moov data.
* This should also handle evil mdat, moov, mdat cases and alike */
gst_adapter_clear (demux->adapter);
gst_adapter_flush (demux->adapter, demux->neededbytes);
/* Store any remaining data after the mdat for later usage */
remaining_data_size = gst_adapter_available (demux->adapter);
if (remaining_data_size > 0) {
g_assert (demux->restoredata_buffer == NULL);
demux->restoredata_buffer =
gst_adapter_take_buffer (demux->adapter, remaining_data_size);
demux->restoredata_offset = demux->offset + demux->neededbytes;
GST_DEBUG_OBJECT (demux,
"Stored %" G_GSIZE_FORMAT " post mdat bytes at offset %"
G_GUINT64_FORMAT, remaining_data_size,
demux->restoredata_offset);
}
gst_adapter_push (demux->adapter, demux->mdatbuffer);
demux->mdatbuffer = NULL;
demux->offset = demux->mdatoffset;
@ -4861,6 +4883,16 @@ gst_qtdemux_chain (GstPad * sinkpad, GstObject * parent, GstBuffer * inbuf)
/* need to resume atom parsing so we do not miss any other pieces */
demux->state = QTDEMUX_STATE_INITIAL;
demux->neededbytes = 16;
/* check if there was any stored post mdat data from previous buffers */
if (demux->restoredata_buffer) {
g_assert (gst_adapter_available (demux->adapter) == 0);
gst_adapter_push (demux->adapter, demux->restoredata_buffer);
demux->restoredata_buffer = NULL;
demux->offset = demux->restoredata_offset;
}
break;
}
}

9
gst/isomp4/qtdemux.h
View file

@ -91,6 +91,15 @@ struct _GstQTDemux {
GstAdapter *adapter;
GstBuffer *mdatbuffer;
guint64 mdatleft;
/* When restoring the mdat to the adatpter, this buffer
* stores any trailing data that was after the last atom parsed as it
* has to be restored later along with the correct offset. Used in
* fragmented scenario where mdat/moof are one after the other
* in any order.
*
* Check https://bugzilla.gnome.org/show_bug.cgi?id=710623 */
GstBuffer *restoredata_buffer;
guint64 restoredata_offset;
guint64 offset;
/* offset of the mdat atom */