[linux-dvb] Re: channels.conf syntax?

[John Dalgliesh <johnd@syd.microforte.com.au>]

On Wed, 19 Nov 2003, Jamie Honan wrote:

> 
>  ... much good stuff elided ...
> 
> > Which means to scan the range +/- 150kHz around each frequency (unless
> 
> Isn't it +/- 125 Khz?

Whoops, yeah, that too... Ahem. (not so good at this working from memory
thing - at least I got channel 6 right :) [Pretty sure it's +/- 166667 
Hz for the UK too...]

> I was going to use something like this, in scconf format:
> 
> tune_possibilities Australia {
>         type = "TV";
>         offsets = 0,-125,125;
>         bandwidth = "7Mhz";
>         frequencies = 177500, 184500, 191500, 198500, 212500, 219500,
> 226500, 529500, 536500, 543500, 550500, 557500, 564500, 571500, 578500,
> 585500, 592500, 599500, 606500, 613500, 620500, 627500, 634500, 641500,
> 648500, 655500, 662500, 669500, 676500, 683500, 690500, 697500, 704500,
> 711500, 718500, 725500, 732500, 739500, 746500, 753500, 760500, 767500,
> 774500, 781500, 788500, 795500, 802500, 809500, 816500;
> }

Mmmmm, pretty and compact. XML is neither of those things.

> I've started documenting scconf. Here is my tongue-in-cheek
> introduction:
> 
...
> 
> Why doesn't it have X, why don't you use XML?
> =============================================
> 
> Maybe it should. Maybe XML is the answer. Maybe a database is more
> appropriate.

Just because you use XML doesn't mean you need to link against a huge
library. In my day job we use XML to describe game objects, model node
hierarchies, settings files, etc. - pretty much anything that isn't a big
block of binary data, i.e. a texture or a triangle array. We make minor
changes to file formats quite a bit, usually for adding features.

To parse the XML, we started off with linking against an XML parsing
library (I think it was Xerces - this was in 2000 or 2001 'tho). It was
huge and slow. So we decided to write our own and stick to a subset of
XML: No attributes in tags and only one text string associated with each
tag (which must come before any child tags).

This made the parsing of the file really fast and easy, and the code to do
it is very small. But it still meant we can edit and verify our files with
any XML editor, since it is still legal XML (although vim/Notepad remains
the most popular editor :)

> It's all a trade-off. You choose. This is only a document.

I think if you agree to use a subset of XML, you can write your own parser
with no more difficulty than you would for any other file format, while
keeping all the benefits and fuzzy goodness of XML :) [Although I note
that scconf has data types built in, which is not the case with XML]

> Jamie

{P^/



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