[Bug 702725] New: first-class miniobjects/API for mpeg-ts related SI (Service Information)

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=702725
  GStreamer | gst-plugins-bad | git

           Summary: first-class miniobjects/API for mpeg-ts related SI
                    (Service Information)
    Classification: Platform
           Product: GStreamer
           Version: git
        OS/Version: Linux
            Status: NEW
          Severity: enhancement
          Priority: Normal
         Component: gst-plugins-bad
        AssignedTo: gstreamer-bugs at lists.freedesktop.org
        ReportedBy: bilboed at gmail.com
         QAContact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---


Several issues arise right now in regards to handling mpeg-ts/DVB SI.

1) performance

  In order for the various SI to be usable by applications, we currently parse
and store them in GstStructures using generic GValue (uint, string, arrays,
lists, ...). This represents over 95% of the cost of parsing those SI !
  And the parsing is equally as expensive.

2) Using glib deprecated items.

  GValueArray is deprecated in glib (sigh) and is ill-suited for the kind of
arrays/collection we want to expose/use.

3) Usability

  If we want to later allow apps to "inject" SI into mpegtsmux, they need to
know exactly the topology of the structure to inject.
  Instead of that, there should be a clear API with structures to fill in.
  In addition, apps need to know what field they should extract, what the type
should be, ....

======

 To this end, I think we should switch to a public API for the various mpeg-ts
SI along with registered mini-objects.
 Ideally this should be supported by g-i also (which should work if we register
boxed GType for each of them).

The "hierarchy" could look something like this:

GstMiniObject
  +-- MpegTSSection
     +-- MpegTSPAT
     +-- MpegTSNIT
     +-- MpegTSEIT
      .....

MpegTSSection {
  GstMiniObject parent;

  gint16   pid;
  guint8   table_id;
  guint16  subtable_extension;
  guint8   version_number;
  guint8   current_next_indicator;
  guint8   section_number;
  guint8   last_section_number;
  guint32  crc;
}

MpegTSPAT {
  MpegTSSection parent;

  guint16  transport_stream_id;
  guint16  nb_programs;
  ....
}


In addition, we could expose descriptors in a cleaner way (avoiding string
copies also)

GstMpegTSDescriptors {
  const guint8 *backing_string;
  guint nb_descriptors;
  GstMpegTSDescriptor descriptors[]; /* Null-terminated array */
}

GstMpegTSDescriptor {
  guint8 descriptor_tag;
  guint8 descriptor_length;
  const guint8* descriptor_content; /* pointer to descriptors->backing_string
*/
}

and expose the various macros to parse them.

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