Understanding GstBaseSrc Create function

[Tim Müller]

On Mon, 2014-10-27 at 22:46 -0700, HK wrote:

Hi,

> I am new to gstreamer. I was going through the filesrc plugin. Here I came
> across the create function. In this create function we have a buffer, and
> the data which is to be pushed to the other element is copied to the
> gstreamer buffer in this create function. I have couple of questions
> regarding this scenario.
> 
> 1. Who will invoke the create function ? Is it invoked by the next element
> or is it invoked by the application ? Or is it something like if the
> application is changing the state, automatically this create function is
> called ?

It's invoked by the GstBaseSrc base class, which basically starts a
thread that does:

  while (run) {
    buf = create()
    push_buffer (buf);
  }

> 2. Once the create method is called, the data buffer has to go to the other
> element ( say for example demux ). Will the input buffer from the file
> source is processed by the chain function of demux ? How the buffer is
> passed to the demux element ?

output buffer you mean presumably? The buffer is passed to the next
element (e.g. a demuxer) by the base class via gst_pad_push().

Cheers 
-Tim

> Thanks
> HK
> 
> 
> 
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-- 
Tim Müller, Centricular Ltd - http://www.centricular.com