[PATCH videoproto] Xvproto: fix xvEncodingInfo to match actual wire protocol

[Kevin Ryde]

Julien Cristau <jcristau at debian.org> writes:
>
> Both it and libXv use sz_xvEncodingInfo, which is ok.

Am I right code is always supposed to use the "sz_" constants, not
sizeof?  Not that that would be an excuse to break anything.

If in doubt I suppose could put the intended pad before, but leave the
pad at the end as well so the sizeof is unchanged.  Not matching the
sz_, but at least not changed.