[vlc-devel] [PATCH] esformat/transform work resubmission

[Lyndon Brown]

Resubmitting this now what with someone trying to add a transform
property to demux-mock and AJ having filed a couple of bugs recently
relating to transformations. If correctness of transformations is under
investigated, then there's more pressure to get my fixes to the core
functionality in place.

I've put the work on a clean branch here (13 commits):
https://code.videolan.org/jnqnfe/vlc/-/tree/transform

 - **fixes the broken core transform functions.**
 - adds a test unit to prove soundness.
 - fixes mistakes in documentation and otherwise improves it.
 - fixes an unnecessary O->T->O translation.
 - fixes an unnecessary format object copying.
 - improves clarity of transform enum variants (resulting from my own
confusion in getting my head around it as it was).
 - other misc. tidying.
 - removes an unused struct property from transform plugin.

Differences since previous submission:

 1. I have included a test unit comprehensively covering all
transformations. This proves conclusively the brokenness of the
existing functions and the soundness of the fix, addressing previously
raised suggestion that the new solution looked possibly faulty.

 2. Minor tweaks.