[gst-devel] Gst-omx buffer renegotiation problem

[Rob Clark]

On Aug 1, 2010, at 11:59 AM, Mikko Hurskainen wrote:

> Hi all,
> 
> I ran into a buffer renegotiation problem when trying to use gst-omx.
> Since I didn't found any other mailing list for gst-omx and the problem
> might be relevant for other gstreamer components as well I am posting my
> question here.
> 
> So the problem is that when using the gst-omx video decoding the buffers
> are allocated automatically. The gst-omx queries from the component that
> how many and which size buffers it should allocate. The omx component
> replies to allocate very few and very small buffers. With those buffer
> sizes the decoding cannot proceed (input 2 buffers of size 256 and
> output 4 buffers of size 256).


I think normally the input port params should be set already, before buffers are allocated..  so the OMX component should be able to return sensible buffer sizes before gst-openmax transitions into executing state (and allocates buffers as part of that transition).

So I'm tempted to call this a bug in your OMX component.  But including a log with "*omx*:5" traces would be helpful to see exactly what is going on.


BR,
-R


> 
> When gstreamer does the preroll and the component starts decoding it
> posts settings changed event that contains the correct sizes of the
> buffers for input & output. The settings changed event is handled in the
> base_video_dec class, but only for resolution & color format.
> 
> So far I've identified two solutions:
> - Always at the beginning allocate a big enough buffer, however, this
> solution has a drawback when dealing with HD resolutions
> - Implement buffer reneallocation into the base_video_dec class.
> 
> The buffer reallocation seems to be the way to go, but before jumping
> into this I would like to ask if anybody else has encountered the same
> problem with some non-omx codec and how it was handled ? For example
> which state the gstreamer pipeline needs to be and so on ? Normally of
> course media file container provides these values, but sometimes that
> might be broken and/or unavailable.
> 
> -- Mikko Hurskainen
> 
> 
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