[linux-dvb] Re: Section Filters

[Johannes Stezenbach <js@convergence.de>]

Hakenes Rolf wrote:
> 
> I'm experimenting with the DVB-SI datastream for quite a long time now in
> order to extract useful information out of it. Dealing with this some
> questions came up concerning the meaning and usage of the API built-in
> section filter mechanism. Both APIs provide (theoretically)  the possibility
> to define a mask value on a specified TID as well as multiple TIDs (up to 16
> AFAIK) per filter. Unfortunately I was not able to get any working setup for
> a filter using these (undocumented) features. Therefore I'd like to ask
> someone (who possibly knows) about the meaning and implementation status of
> the described fields of the filter structures.

Here's what's missing from the documentation of the demux device
of the new API:

--------
The dmxFilter structure defines a section filter, i.e. a bit pattern
and a mask for the first bytes of a section. The filter comprises
16 bytes covering byte 0 and bytes 3..17 in a section, thus excluding
bytes 1 and 2 (the length field of a section).

The mask states which bits to be used for filtering, and the filter
states the actual value of these bits. Only the value of the bits
where the corresponding mask bit is 1 will be checked.
--------

Byte 0 in the filter is the table id.


Johannes


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