videometa: document how the meta can be used to negotiate buffers layout

I'm going to use this new API in gst-omx so an encoder can request
v4l2src to produce buffers matching the encoder stride and slice heights
preventing copies of incoming buffers.
This commit is contained in:
Guillaume Desmottes 2019-05-25 19:23:35 +02:00 committed by GStreamer Merge Bot
parent a32cd0e55e
commit e5c9a921ad

View file

@ -59,6 +59,21 @@ typedef struct _GstVideoCropMeta GstVideoCropMeta;
* to no padding and no alignment. Since: 1.18
*
* Extra buffer metadata describing image properties
*
* This meta can also be used by downstream elements to specifiy their
* buffer layout requirements for upstream. Upstream should try to
* fit those requirements, if possible, in order to prevent buffer copies.
*
* This is done by passing a custom #GstStructure to
* gst_query_add_allocation_meta() when handling the ALLOCATION query.
* This structure should be named 'video-meta' and can have the following
* fields:
* - padding-top (uint): extra pixels on the top
* - padding-bottom (uint): extra pixels on the bottom
* - padding-left (uint): extra pixels on the left side
* - padding-right (uint): extra pixels on the right side
* The padding fields have the same semantic as #GstVideoMeta.alignment
* and so represent the paddings requested on produced video buffers.
*/
struct _GstVideoMeta {
GstMeta meta;