[gst-devel] empty buffers & GST_BUFFER_FLAG_GAP

Stefan Kost ensonic at hora-obscura.de
Wed Jan 18 12:01:05 CET 2006

Hi Jan & Wim,
Jan Schmidt wrote:
> On Wed, 2006-01-18 at 17:36 +0100, Stefan Kost wrote:
>>I think there are use-cases for both applications. I'd like to read your design 
>>document and then continue the discussion.
> I just added a first draft of the idea in
> docs/design/part-sparsestreams.txt (in core)
I've just read

Thanks for adding my use case to it. Still I don't see how it will work. Imagine 
the following pipeline:

simsyn ! echo ! audiosink

simsyn is somthing like audiotestsrc, but instead of a freqeuncy you give it a 
musical note (c-3). The note will be set via GstController from time to time. 
Setting a note also triggers simsyn volume envelope. In the _create() function 
simsyn checks the envelope level before rendering a buffer. Whenever the level 
go close to zero it just create silent buffers (avoid calculating sines etc.).

Next in the pipeline is the (imaginary) echo element. An echo is usaly 
implemented by using a ringbuffer, where data output-data gets feedback into the 
ringbuffer. This produces decaying echos.

When simsyn determines it produces silence, I still want echo to be called, as 
echo still has data to produce. When echo finds out that the output level from 
the ring-buffer goes below zero it can mark output as silent too and remember 
the state. If next silent buffer are comming, it can just output silence too.

I don't know if this can be done with the technique you've described in the 
part-sparsestreams.txt. Unfortunately I don't know about the 'SCR in MPEG data' 
so I can't map the 'for audio, 3) is the same case as in 1)'.


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