[linux-dvb] Re: PAT/PMT decoding

["Andy Coates" <andy@bribed.net>]

>> On Fri, Jan 31, 2003 at 10:53:22AM -0000, Andy Coates wrote:
>>> 
>>> I'm going insane trying to find documentation on the PAT/PMT data
>>> structures (similar to the SI information for descriptors found in
>>> ETSI EN 300 468). 
>>> 
>>> Does anyone on here know which documents I should be looking at?
>> 
>> The MPEG-2 spec, ISO-13818-1 (aka ITU-T H.222).
> 
> Perfect, thanks guys.

Carrying on from this, can someone who's used to decoding these tables
tell me if the following hex dump of part of a TS packet (PID 0) is
producing a PAT section_number and last_section_number of 0?

	47 40 00 1f 00 00 b0 2d 07 f3 ef 00 00 00 00 e0 10 12
	08 e1 04 14 56 e1 03 14 78 e1 06 14 79 e1 07 14 ab e1
	05 15 82 e1 00 16 aa e1 02 16 ac e1 01 94 71 3f de ff
	(rest is padded with ff)

Looking at the structure, the 8th byte above would be the
section_length, which is apparently 45 in this case (0x2d).
Transport_stream_id would be 0x07f3, and the version_number would be
(0xef & 0x3E = decimal 46).  The next 2 bytes are therefore 00 and 00,
which represent the section_number and last_section_number.

Since there's no difference in the section numbers, there's no loop to
iterate through to produce the association tables.

I've also run decode_pat (from libdvbpsi) on that stream, and it shows
the version_number to be 23 and does list quite a few program_number's
(as if there is some data to iterate through).

So have I decoded that packet wrong?

Sorry if this is off topic, I can't think of anywhere else that would
deal with this sort of programming.

Thanks,
Andy. 



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