Re: Proposal from HbbTV

On 2014-10-14, at 17:13 , Bob Lund <B.Lund@CableLabs.com> wrote:

>> [...]
>> The original_network_id is buried in data structures in MPEG tables. So
>> you would need to make a reasonable guess about which format the table
>> payload has, before being able to parse out the original_network_id.
>> Catch 22.
> 
> Why is guessing involved? Each section/table starts with a table ID field
> which identifies the type of table. It should be deterministic to find the
> original_network_id: the PAT identifies the PID carrying the NIT which,
> according to DVB-SI, carries the network information section with the
> original_network_id for each TS.

Since both, DVB and ISDB use the network PID mechanism, you would need to feed the table you receive through both the DVB NIT parser, and the ISDB NIT parser, and then decide which one delivers more credible results (e.g. based on number and/or severity of parsing errors). I.e. a prior knowledge of whether the TS originates from a DVB or an ISDB system is required.

>> [...]
>> Unfortunately there is nothing that the UA can count on.
>> 
>> With that said, it doesn't mean that it couldn't relatively easily be put
>> there. My suggestion would be for W3C to be in touch with ATSC, DVB, and
>> ISDB and propose to them making the transmission of the TSDT mandatory in
>> their specifications, and put a transport_stream_descriptor in it to
>> allow receivers to unambiguously identify the system type. I shall be
>> happy to help you crafting the message.
> 
> How about HbbTV making a recommendation to DVB, citing the Web use cases
> wešve been discussing. I would be happy to work with you on that.
> [...]

What about making it a joint message between HbbTV and the Inband Tracks Community Group then? ;-)

  --alexander

Received on Wednesday, 15 October 2014 10:26:13 UTC