[Bug 614479] [mpegtspacketizer] Use CRC to check if tables are duplicate

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=614479
  GStreamer | gst-plugins-bad | git

--- Comment #3 from Edward Hervey <bilboed at gmail.com> 2013-06-19 18:46:34 UTC ---
Created an attachment (id=247280)
 View: https://bugzilla.gnome.org/attachment.cgi?id=247280
 Review: https://bugzilla.gnome.org/review?bug=614479&attachment=247280

mpegtspacketizer: Better detect already seen section

In some cases (NIT on highly-populated DVB-C operator for example), there
will be more than one section emitted for the same subtable and version
number.

In order not to lose those updates for the same version number, we checked
against the CRC of the previous section we parsed.

The problem is that, while it made sure we didn't lose any information, it
also meant that if the same section came back (same version, same CRC) later
on we would re-process it, re-parse it and re-emit it.

This version improves on that by keeping a list of previously observed CRC
for identical PID/subtable/version-number and will only process sections if
they really were never seen in the past (as opposed to just before).

On a 30s clip, this brings down the number of NIT section parsing from 4541
down to 663.

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