DVB Tables

[Russel Winder]

On Fri, 2017-05-26 at 08:01 +0200, Edward Hervey wrote:
> 
[…]
>   I did my best to make it a 1:1 mapping with the field naming in the
> specs. Which part don't you think is similar ?
> 

It may well be then that I am just misunderstanding – actually I hope
so, as it will easier to fix that. :-)

The standard presents an EIT section as follows (Table 7 of the
standard):

    event_information_section(){
      table_id
      section_syntax_indicator
      reserved_future_use
      reserved
      section_length
      service_id
      reserved
      version_number
      current_next_indicator
      section_number
      last_section_number
      transport_stream_id
      original_network_id
      segment_last_section_number
      last_table_id
      for(i=0;i<N;i++){
        event_id
        start_time
        duration
        running_status
        free_CA_mode
        descriptors_loop_length
        for(i=0;i<N;i++){
          descriptor()
        }
      }
      CRC_32
    }

The GstMpegtsEIT structure is though:

    struct GstMpegtsEIT {
      guint16        transport_stream_id;
      guint16        original_network_id;
      guint8         segment_last_section_number;
      guint8         last_table_id;

      gboolean       actual_stream;
      gboolean       present_following;

      GPtrArray     *events;
    };

which doesn't seem to map to any bits of the standard's Table 7 –
though it is clear that the events, a sequence of GstMpegtsEITEvent
structures does somewhat map to the N events in the section:

    struct GstMpegtsEITEvent {
      guint16      event_id;

      GstDateTime *start_time;
      guint32      duration;

      GstMpegtsRunningStatus running_status;
      gboolean     free_CA_mode;

      GPtrArray   *descriptors;
    };

My code is getting the events, seemingly correctly (*), but it is the
SID and stuff like that that give the channel numbers that I cannot see
how to extract. The EIT section should have the service_id, but the
GstMpegtsEIT structure does not appear to offer it.

I guess I had expected the GStreamer structures to map more or less
exactly to the tables in the standard, but this seems to be only
partially true. Where it is true, it is easier to work things out.
Where it apparently is not the case, I am at a bit of a loss as to how
to proceed processing the events on the bus so as to collate the data
into an in-memory representation of the EIT.



(*) Though I regularly get memory errors due to all the malloc and free
stuff that I really do not properly understand yet. Oh for doing this
in D with it's garbage collector.

-- 
Russel.
=============================================================================
Dr Russel Winder      t: +44 20 7585 2200   voip: sip:russel.winder at ekiga.net
41 Buckmaster Road    m: +44 7770 465 077   xmpp: russel at winder.org.uk
London SW11 1EN, UK   w: www.russel.org.uk  skype: russel_winder
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