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author | Vivia Nikolaidou <vivia@ahiru.eu> | 2021-08-16 18:15:42 +0300 |
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committer | GStreamer Marge Bot <gitlab-merge-bot@gstreamer-foundation.org> | 2021-10-29 12:42:23 +0000 |
commit | 5c000cb023618bc566748c024a2742bea9df6bc5 (patch) | |
tree | cb222484cffa7a9c158828833611e390ccb9e73c | |
parent | 54029f8fd14268214621daa4ff09b1699029e3b3 (diff) | |
download | gstreamer-plugins-bad-5c000cb023618bc566748c024a2742bea9df6bc5.tar.gz |
mpegtspacketizer: memcmp potentially seen_before data
Theoretically the version number is incremented every time there's a new
section, but in a world of streaming we can't easily make that
assumption.
An example of a broken use case is when we're cat-ing two mpeg-ts files
together, which is equivalent of capturing a DVB stream while switching
channels. A set-top box would know that we switched the channels and
reset the demuxer, but in practice this might not happen.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/2555>
-rw-r--r-- | gst/mpegtsdemux/mpegtspacketizer.c | 17 |
1 files changed, 14 insertions, 3 deletions
diff --git a/gst/mpegtsdemux/mpegtspacketizer.c b/gst/mpegtsdemux/mpegtspacketizer.c index 91df87f90..21d10e7d2 100644 --- a/gst/mpegtsdemux/mpegtspacketizer.c +++ b/gst/mpegtsdemux/mpegtspacketizer.c @@ -154,7 +154,7 @@ find_subtable (GSList * subtables, guint8 table_id, guint16 subtable_extension) static gboolean seen_section_before (MpegTSPacketizerStream * stream, guint8 table_id, guint16 subtable_extension, guint8 version_number, guint8 section_number, - guint8 last_section_number) + guint8 last_section_number, guint8 * data_start, gsize to_read) { MpegTSPacketizerStreamSubtable *subtable; @@ -175,7 +175,17 @@ seen_section_before (MpegTSPacketizerStream * stream, guint8 table_id, return FALSE; } /* Finally return whether we saw that section or not */ - return MPEGTS_BIT_IS_SET (subtable->seen_section, section_number); + if (!MPEGTS_BIT_IS_SET (subtable->seen_section, section_number)) { + GST_DEBUG ("Different section_number"); + return FALSE; + } + + if (stream->section_data) { + /* Everything else is the same, fall back to memcmp */ + return (memcmp (stream->section_data, data_start, to_read) != 0); + } + + return FALSE; } static MpegTSPacketizerStreamSubtable * @@ -1189,7 +1199,8 @@ section_start: * * same section_number was seen */ if (seen_section_before (stream, table_id, subtable_extension, - version_number, section_number, last_section_number)) { + version_number, section_number, last_section_number, data_start, + to_read)) { GST_DEBUG ("PID 0x%04x Already processed table_id:0x%02x subtable_extension:0x%04x, version_number:%d, section_number:%d", packet->pid, table_id, subtable_extension, version_number, |