[gst-devel] Wow! (more questions, sorry :)

[Erik Walthinsen]

On Thu, 11 May 2000, Myers W. Carpenter wrote:

> 	I stayed up late last night reading through the entire mailing list
> archive and all I can say now is WOW.   This is cool.  I'm really
> impresed as to what this framework can do.
Cool! ;-)

> 	I would like to add what I can to the project.  Where can I start?  My
> personal inclination is to write end user apps, and my main itch is a
> good video player with seek support.  I was encouraged by this comment
> (I think it was a cvs commit or something)
That seems to be the current primary direction, so yeah.

> 	Is gstreamer ready for a end user app?  I realize gstreamer is "a
> moving target" but I'm willing keep aiming.  If this really isn't a good
> idea point to where I should go. 
Probably not quite yet.  I'll write up a list of what needs to be dealt
with before we can stabilize on any apps.

> 	Some one asked what kind of documentation would be good, I think top
> down api documentation (gstreamer from an application writer point of
> view.  Check out the docs for libmpeg2 or quicktime4linux for examples)
> would be great.  I would like to do this along the way while writting
> the video player.
Yeah, docs are sorely lacking (though Wim did a great job at updating the
inline API docs).  I've sat down and tried to write a top-down intro, but
I'm so familiar with it that I can't stay at the simplest level for more
than about 3 words.  Having someone who's learning it at the same time
write out the docs is generally a good idea, so if you want to take a
crack at it, please, be my guest ;-)

> What is scrubbing ?  fast forward, playing backwards?
'Scrubbing' in media editting is simply the ability to scan through the
timeline arbitrarily.  In hardware solutions, such as story-editting
systems used at TV stations, they use a jog-shutting on steroids for the
task, where they have the rotary controls, as well as a speed dial, and a
few others.  I've seen a Windoze editting program use the wheel on a mouse
as a shuttle, it works relatively well.

> What's "UST-style nanoseconds"?
UST stands for Unadjusted System Time, a proposal by SGI to provide some
means of getting a real hardware clock at all times, very inexpensively,
from user-space, at nanosecond (real or faked) resolution, since boot.  On
1.000000000GHz Intel machines, this is rdtscll()....  The idea is that UST
is capable of representing time accurately enough to detect the difference
between 44.1KHz and 44.101KHz.  It's ideal for multimedia, where things
run a different speeds all the time.  MPEG punted somewhat by defining
some bizarre frequency (930KHz or something) that happens to be a multiple
of both the audio and video rates.

I'd like to use UST for timestamping, even if it's not the only format.
There's some expense in doing 64bit math, though...

         Erik Walthinsen <omega at cse.ogi.edu> - Staff Programmer @ OGI
        Quasar project - http://www.cse.ogi.edu/DISC/projects/quasar/
   Video4Linux Two drivers and stuff - http://www.cse.ogi.edu/~omega/v4l2/
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