[gst-devel] Query regarding using videotestsrc with a custom video sink plugin that is capable of allocating "special" (ie. display/hw) buffers

[Wim Taymans]

On Wed, 2009-02-11 at 15:27 +0530, Mohan Krishna wrote:
> Hi
> 
> I am using a custom video sink plugin (which uses V4L2 api internally)
> on an embedded device. This custom sink plugin implements a pad alloc
> function so as to provide hw/display buffers to the upstream peer
> plugin. There is a limit on the number of buffers that video sink
> plugin can allocate (currently 4).
> 
> The pipeline I am using is
> gst-launch videotestsrc !
> 'video/x-raw-yuv,width=(int)1280,height=(int)720,format=(FOURCC)UYVY,framerate=(fraction)30/1'
> ! custom_video_sink
> 
> The issue I am facing is the custom_video_sink plugin runs out of
> buffers as videotestsrc seems to continuously invoke pad_alloc_buffer
> before giving back the buffers for rendering.
> 
> Requesting help from the developer community in addressing this issue.
> What is the general practice used in scenarios where there is a limit
> on the number of "special" buffers that can be allocated by the video
> sink plugin.

The sink simply blocks in its buffer_alloc function until a hardware
buffer becomes available (one is rendered and unreffed back into the
pool or released somewhere else in the pipeline) or when the sink is
shut down.

If you need more buffers (some complex algorithm requiring many buffers)
you can hand out plain, unoptimised buffers if you want. You probably
then need to wait in the _render() function for a hardware buffer to
become available before you can actually render the buffer.

Wim

> 
> Any help would be greatly appreciated
> 
> Thanks and Regards
> Mohan
> 
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