[gst-devel] Audio visualizations

[Stefan Kost]

Am 27.07.2010 18:53, schrieb Matteo Landi:
> Hi guys,
> these days I was wondering how to use gstreamer in order to create
> some audio visualizations like an oscilloscope or a spectrum analyzer.
> 
> The application consist of a window with a drawing area used to
> display the visualizations.
> Regarding the pipeline, I thought about something like
> 
> filesrc !
> decodebin !
> audioconvert !
> audio/x-raw-int, channels=1, rate=44100, width=16, depth=16, endianness=1234 !
> tee name=t !
>   queue !
>     fakesink name=fakesink signal-handoffs=true t. !
>   queue !
>     autoaudiosink
> 
> with the handoff callback linked to a method which spawn a new thread,
> process the signal, and queue a redraw of the window.

Have a look at gst-plugins-good/test/examples/spectrum/

Anyway, don't draw to gtk-windows from a custom thread. Rather do processing in
a gst element and post the data via GstBus to the main thread and draw there.

Stefan

> 
> I got few problems with the implementation:
> 1 - I often get core dumped, and I cannot understand why: all the
> drawing actions are done inside the main thread, so it should be ok
> ...
> 2 - Synchronization between audio and video: the two sources are not
> synchronized.. maybe is it something related to the queues elements?
> 
> Have you got any advices regarding the chosen implementation, and how
> to solve the listed problems?
> 
> Thanks in advance for the attention.
> 
>