[gst-devel] [Fwd: Questions about GStreamer]

[Andy Wingo]

> From: Nick Wellnhofer <wellnhofer at aevum.de>
> Subject: Questions about GStreamer
> Date: Wed, 14 Jan 2004 01:13:12 +0100
> 
> Is it possible to use audio streams with different sample rates? Can you 
> realize something like a pitch effect plugin (with dynamic pitch 
> control), that simply alters the audio playback speed? For example a 
> setup like this:
> 
> +----------------+    +--------------+    +-------+
> | audio source 1 |--->| pitch effect |--->|       |
> +----------------+    +--------------+    |       |
>                                           | mixer |--->
> +----------------+                        |       |
> | audio source 2 |----------------------->|       |
> +----------------+                        +-------+

Hi Nick,

It's not a problem, provided that the two branches really are separate.
Of course, if they are both reading from the same sound card it's
impossible. But what happens is that the nominal sample rate is the same
on both sides of the pitch effect (see the `speed' plugin), but that the
pitch effect can ask for data at whatever rate (relative to the other
side) it likes. There's no "clock tick" that drives the graph; rather,
the mixer receives a request for data, which makes it ask the pitch
effect for data, which makes the pitch effect ask for however much it
wants.

> I know I could find it out by myself reading the docs/source. But 
> chapter 18 of the documentation about clocks which might answer my 
> questions is still empty.

It actually doesn't have anything to do with clocks.

-- 
Andy Wingo <wingo at pobox.com>