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qtdemux: Always check ctts for unreasonably large offsets

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If this happens then ignore the whole ctts. Previously we only did this
if the PTS/DTS shift was determined from the ctts instead of the cslg.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/1294>
This commit is contained in:
Sebastian Dröge 2021-11-12 12:46:56 +02:00 committed by GStreamer Marge Bot
parent 93a10a4ba1
commit ad412d257b
1 changed files with 34 additions and 0 deletions
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34
subprojects/gst-plugins-good/gst/isomp4/qtdemux.c
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@ -9391,6 +9391,7 @@ qtdemux_stbl_init (GstQTDemux * qtdemux, QtDemuxStream * stream, GNode * stbl)
&stream->ctts) ? TRUE : FALSE) == TRUE) {
GstByteReader cslg = GST_BYTE_READER_INIT (NULL, 0);
guint8 ctts_version;
gboolean checked_ctts = FALSE;
/* copy atom data into a new buffer for later use */
stream->ctts.data = g_memdup2 (stream->ctts.data, stream->ctts.size);
@ -9445,6 +9446,8 @@ qtdemux_stbl_init (GstQTDemux * qtdemux, QtDemuxStream * stream, GNode * stbl)
pos = gst_byte_reader_get_pos (&stream->ctts);
num_entries = stream->n_composition_times;
checked_ctts = TRUE;
stream->cslg_shift = 0;
for (i = 0; i < num_entries; i++) {
@ -9477,6 +9480,37 @@ qtdemux_stbl_init (GstQTDemux * qtdemux, QtDemuxStream * stream, GNode * stbl)
/* reset the reader so we can generate sample table */
gst_byte_reader_set_pos (&stream->ctts, pos);
}
/* Check if ctts values are looking reasonable if that didn't happen above */
if (!checked_ctts) {
guint num_entries, pos;
gint i;
pos = gst_byte_reader_get_pos (&stream->ctts);
num_entries = stream->n_composition_times;
for (i = 0; i < num_entries; i++) {
gint32 offset;
gst_byte_reader_skip_unchecked (&stream->ctts, 4);
offset = gst_byte_reader_get_int32_be_unchecked (&stream->ctts);
/* HACK: if sample_offset is larger than 2 * duration, ignore the box.
* slightly inaccurate PTS could be more usable than corrupted one */
if (G_UNLIKELY ((ABS (offset) / 2) > stream->duration)) {
GST_WARNING_OBJECT (qtdemux,
"Ignore corrupted ctts, sample_offset %" G_GINT32_FORMAT
" larger than duration %" G_GUINT64_FORMAT,
offset, stream->duration);
stream->cslg_shift = 0;
stream->ctts_present = FALSE;
goto done;
}
}
/* reset the reader so we can generate sample table */
gst_byte_reader_set_pos (&stream->ctts, pos);
}
} else {
/* Ensure the cslg_shift value is consistent so we can use it
* unconditionally to produce TS and Segment */