appsrc usage (push and pull mode)

[Sebastian Dröge]

On Mo, 2013-10-21 at 07:46 -0700, distran wrote:

> [...]
> Questions:
>   - In "push" mode - how often is actually "push-buffer" signal invoked?
> What, if there are a lot of "higher priority events"? How precisely can we
> control the rate with which "push-buffer" signal is emitted (for the
> pipeline it is usually required to send frames with approximately specified
> rate)?

push-buffer is an action signal, you invoke/emit it and not appsrc. It
happens as often as you do that. And will block if the appsrc buffer
queue is filled until downstream handles another buffer.

>   - What is the difference between g_signal_emit_by_name (app->appsrc,
> "push-buffer", buffer, &ret); and using directly ret =
> gst_app_src_push_buffer(app->src, buffer); ?

None at all

>   - In both modes function, that emits "push-buffer" signal is invoked
> somewhat automatically (in "pull" mode, when we receive "need-data" signal,
> and in "push" mode when there are no higher priority events). Is it possible
> to directly emit "push-buffer" signal when we have our frame ready to emit?
> (as I said before, in my architecture I have an element, that generates
> frames constantly with a certain frame rate. Would it be possible to emit
> "push-buffer" every time frame is generated? What are the drawbacks of such
> solution? - I tried emitting "push-buffer" signal directly from producer
> thread and it seems to work well).

Yes, that's exactly what you should do. Start a thread and from that
thread push buffers to appsrc as fast as possible.

-- 
Sebastian Dröge <sebastian at centricular.com>
Centricular Ltd - http://www.centricular.com
Expertise, Straight from the Source
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