metadata propagation in gsttransform plugins

[Dimitrios Katsaros]

I am not able to find the code implementing that specific encoder on the
fly so I will try and work with whtever assumptions I can make about
encoders in general and your post.

You will need to make sure that your metadata implements a transformation
function, the encoder implements a transformation function and that the
tags of the metadata are correctly set for the specific transformation.
Assuming that the imxvpuenc_mjpeg inherits the videoencoder class and does
not override the transform_meta function, you will need to make sure that
the meta tags include "video" and do *not* include "memory"


Dimitrios

On Thu, Jan 19, 2017 at 12:47 AM, Philippe De Muyter <phdm at macq.eu> wrote:

> Hi all,
>
> I have read that since the 1.6 version of gstreamer frame tags are
> preserved
> by each plugin.  My questions below are targeted at the propagation by
> GstVideoEncoders of memory- and frame-size- independent tags, such as gps
> data,
> exposure, gain that could vary from frame to frame, and so on.
>
> I have the following pipeline :
>
> gst-launch-1.0 imxv4l2videosrc ! tee name=t ! queue ! \
>         imxvpuenc_mjpeg ! mprintmeta logname=1 ! fakesink i\
>         t. ! queue ! imxvpuenc_h264 ! mprintmeta logname=2 ! fakesink
>
> where imxv4l2videosrc has been modified to add custom metadata, and
> mprintmeta is debugging to show those metadata.  I notice that the
> metadata are not present after the encoders
>
> - Is the propagation mechanism implemented outside of the plugins, or must
> it be implemented in each plugin ? In that case, is a generic propagation
> code
> available, that we could add e.g. to gstreamer-imx (imx hardware
> accelerated)
> encoder plugins ?
>
> - Is GstMetaFreeFunction only called after all instances are unused, or is
> there a refcount accessible inside the definition of GstMetaFreeFunction
> for a new metadata type, to avoid that one branch after a 'tee' destroys a
> metadata that's still used by the other branch ?
>
> Thanks in advance
>
> Philippe
>
> --
> Philippe De Muyter +32 2 6101532 Macq SA rue de l'Aeronef 2 B-1140
> Bruxelles
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