[Bug 732542] New: h264parse: drop broken SEI NAL units/messages?

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=732542
  GStreamer | gst-plugins-bad | git

           Summary: h264parse: drop broken SEI NAL units/messages?
    Classification: Platform
           Product: GStreamer
           Version: git
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gst-plugins-bad
        AssignedTo: gstreamer-bugs at lists.freedesktop.org
        ReportedBy: gb.devel at gmail.com
         QAContact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---


Hi, the current implementation of gst_h264_parse_process_sei() will ignore any
error from badly constructed SEI NAL unit. i.e. in alignment=au mode, we will
be accumulating broken SEI NAL units.

There are multiple (non-?) issues here:

1. If the SEI NAL unit contains a single SEI message that is incorrectly
constructed, the process_sei() function would ignore it. It could be
interesting to skip it from the output.

2. If the SEI NAL unit contains multiple SEI messages, and one of the SEI
message is badly constructed, what should we do? Rejecting the whole NAL unit
wouldn't be appropriate. However, would it be worth recreating a correct NAL
unit with the good SEI messages? Otherwise, it could be just fine to delegate
that to the decoder, and let it care, if needed.

3. In the codec parser, we try very hard to make the parser robust with invalid
SEI messages. In particular, if the reported payloadSize is larger than what is
left in the NAL unit, we would just skip the message, unless it is one of the
supported set. Is it worth reporting an appropriate error?

Thinking further, I think this bug is totally useless after all, and it might
be just fine to ignore any SEI related error. :) That's supplemental
information that does not interfere in the core decoding process. So, an error
could be bearable.

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