Fwd: [gst-devel] newbie questions

[Edward Hervey]

Forgot to forward the mail to the mailing list

---------- Forwarded message ----------
From: Edward Hervey <bilboed at gmail.com>
Date: May 24, 2005 4:01 PM
Subject: Re: [gst-devel] newbie questions
To: Akos Maroy <darkeye at tyrell.hu>


Hi,

On 5/24/05, Akos Maroy <darkeye at tyrell.hu> wrote:
> Hi,
>
> I'm new to gstreamer, and I have a few questions, which I'm sure you'll
> find very basic, but I couldn't myself find the answer for.
>
>
> - difference / converting between audio/x-raw-int and audio/x-raw-float
>
> I see that some audio related plugins use x-raw-int, some use
> x-raw-float as the raw audio format. is there a plugin that would
> convert between these two formats?
>
> for example, vorbisdec has a 'src' pad in x-raw-float format, but for
> osssink (or volenv) only support x-raw-int
>
>
> - how to write a play offset plugin?
>
> I'd need the following functionality: for an input, I'd either need to
> play only a portion, or I'd need to add extra silence before or after
> the input.
>
> for example, say I have a 60 second audio input, I need to play it as
> follows:
>
>     - only play from the 5th second up to the 45th second,
>       making it a 40 second input
>
>          +--------- 60 second input -----------------+
>             +---- 5th to 45th second ---------+
>
>     - start playing only 11seconds later, and after the 60secs, have
>       a 5second silence afterwards, making it a 76second input
>
>            +--------- 60 second input -----------------+
>   +-11sec-++--------- 60 second input -----------------++-5sec-+
>
>
> I wonder how this could be achieved with a plugin (or if there's already
> a plugin that achieves this functionality). why I'm wondering is that
> the chains channel data through the whole chain, but here a plugin
> making the above functionality available whould need to act to some
> extent without receiving input on its sink.
>

  You might want to have a look at the Gnonlin library, based above
GStreamer, which is aimed at creating audio/video non-linear editors,
but which also fits your need.

  With your given example you use 3 GnlSource : 2 with the silence
source in it (silence1 and silence2), and one with your real source in
it (mysource).
 Set silence1 properties as follow :
    start=0, stop=11*GST_SECOND
 Set silence2 properties as follow :
    start=51*GST_SECOND,stop=56*GST_SECOND
 Set mysource properties as follow :
    start=11*GST_SECOND,stop=51*GST_SECOND,
    media_start=5*GST_SECOND,media_stop=45*GST_SECOND

 Add those gnlsource to a Gnlcomposition, and add that composition to
a GnlTimeline. You can now use that timeline as a source that
automatically switches to the good source depending on where you want
to seek.

 GNonLin's API details it a bit further, but that should get you starting.

 Gnonlin website : http://gnonlin.sf.net/

  Edward,

>
> Akos
>
>
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