[gst-devel] stride

[Thomas Vander Stichele]

Hi,

while working on pixel aspect ratio stuff I ran into a problem that I'm
not sure how we would want to handle it.

The problem I was having was that a video was being scaled to 1015x432. 
Now when ximagesink was allocating buffers for this, the XShmCreateImage
call gives you back a bytes_per_line property (which is video stride),
and expecting it to be respected.  However, GStreamer was not feeding
ximagesink data respecting the rowstride.

So I started thinking about it some more, and read some code.

- do we have an explicit or implicit definition of how data should be
laid out in both RGB and YUV ?
- videotestsrc implicitly seems to output data with rowstride in my
particular test case.  Can we trust videotestsrc to be doing the correct
thing or should I doublecheck it for all cases ?
- should rowstride be part of the caps (at least in cases where the
rowstride is not the one that you would implicitly assume) ?
- is it ok for ximagesink at runtime to figure out the rowstride, add it
to the caps, and renegotiate its link ?
- If we add it to the caps, should we add 3 of them for YUV data ?
- Is it ok to make colorspace and videoscale elements to handle
rowstride correctly ?

Let me know so I can fix it properly together with PAR code.

Thomas

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