[Vorbis] Re: Write pure sine to *.ogg directly?

[Gan Uesli Starling]

Monty writes:
> 
> On Mon, Feb 20, 2006 at 09:39:35AM -0500, Gan Uesli Starling wrote:
>> I'd like some means of writing a pure sine wave straight
>> to *.ogg just as I currently can to *.wav (using the Perl
>> Audio::Wav module). 
> 
> Slightly more fundamnetally complex, but it wouldn't bee too hard if
> you're not *too* picky about the *exact* frequency you want to output.

Anywhere in the range of 750 Hz to 800 Hz is close enough. All that counts
is that it not waver to the human ear. 

> What will probably suck, though, is getting ahold of a perl binding
> for libogg and enough of libvorbis to set a few packet fields. 
> 
>> This would involve turning on and off a sine wave of N mS
>> duration with silences between. And the leading edges of
>> these sine-wave segments require a not-too-abrupt rise time
>> to avoid what Morse folks call "key clicks" and, if I read
>> correctly, cause "pre echos" in compressed audio. 
> 
> I'd expect you'd want to build the tone packets directly from the
> spectral math you'd need for a given sine wave; preecho would be
> vaguely irrelevant.

I can define a sine wave in Perl easily enough, or a haversine, or
a bezier. Have done all three previously. 

>> Bearing in mind that I know nothing about audio codecs beyond
>> being able to use Perl's Audio::Wav module, have I any hope of
>> accomplishing such a task in Perl with output direct to *.ogg?
>> Where would I start in such a case? 
> 
> Yes... but it depends on what perl bindings already exist.  Building
> the vorbis packets in Perl wouldn't be too bad (I expect you only need
> a couple 'canned' packets), but stitching them into the Ogg stream
> would require a bit more code if Ogg code isn't already available.

They have some Perl modules for parsing and editing Ogg tags. But all
I have seen otherwise were just wrappers for oggenc. Guess I need to
have a look at the Ogg file format, encode some morse from *.wav using
oggenc and see if I can grok the result. Did that once for an automotive
road load data acquisition format. It took forever and wasn't fun. But
the result was worthwile...in fact, I use it quite a lot. 

What docs ought I read first? And where might I find them? 

Thanks, 

Gan Starling, KY8D
Kalamazoo MI USA