[Bug 752161] New: ac3parse: Apply the loosen parsing policy

[GStreamer (GNOME Bugzilla)]

https://bugzilla.gnome.org/show_bug.cgi?id=752161

            Bug ID: 752161
           Summary: ac3parse: Apply the loosen parsing policy
    Classification: Platform
           Product: GStreamer
           Version: unspecified
                OS: All
            Status: NEW
          Severity: normal
          Priority: Normal
         Component: gst-plugins-good
          Assignee: gstreamer-bugs at lists.freedesktop.org
          Reporter: kyungyong.kim at lge.com
        QA Contact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---

Created attachment 307131
  --> https://bugzilla.gnome.org/attachment.cgi?id=307131&action=edit
ac3parse: Apply the loosen parsing policy

According to A/52 Annex E, the bsid field in header may be greater than 16.
Thus, decoders compliant with this Annex shall mute if the value of bsid is 9,
10, or greater than 16.
But, ac3parse doesn't accept the value of bsid is greater than 16.
gst_ac3_parse_frame_header () returned FALSE for those frames and discarded
them.
We apply the loosen parsing policy rather than the strict parsing policy.

------------------------------
A/52 Annex E (17 December 2012)

2.3.1.6 bsid – Bit Stream Identification – 5 Bits
The bsid field has a value of ‘10000’ (=16) for bitstreams compliant with this
Annex. Values of smaller than 16 and greater than 10 are used for versions of
E-AC-3 which are backwards compatible with version 16 decoders. Decoders which
can decode version 16 will thus be able to decode version numbers less than 16
and greater than 10. Additionally, E-AC-3 decoders shall also be able to decode
AC-3 bitstreams with bsid values 0 through 8. Decoders compliant with this
Annex are not able to decode bit streams with bsid =9 or 10. Thus, decoders
compliant with this Annex shall mute if the value of bsid is 9, 10, or greater
than 16, and shall decode and reproduce audio if the value of bsid is 0 – 8, or
11 – 16.
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