[FFmpeg-devel] [PATCH 1/3] lavu: Add AVSphericalMapping type and frame side data

[Vittorio Giovara]

On Sun, Nov 13, 2016 at 11:57 AM, Michael Niedermayer
<michael at niedermayer.cc> wrote:
> On Sun, Nov 13, 2016 at 10:18:18AM +0100, Michael Niedermayer wrote:
>> On Sat, Nov 12, 2016 at 10:05:22PM -0500, Vittorio Giovara wrote:
>> [...]
>> > So I really do not see a use case for using int64 here.
>>
>> then you can use int32, less than int32 is too little if for example
>> you wnat the precission to be sufficient to know where a tele lens
>> points with pixel precission and have a bit precission headroom

Hi Michael, thanks for keeping me in CC.
I understand the problem, but this is a solution for a issue that is
non-existent. There is no application or usecase for "pixel perfect"
precision, the rendering of a spherical video will distort the video
surface in order to map the flat surface to a sphere, and it is
impossible to predict where this operation will move pixels to. I
believe this is why this specification describes the initial
orientation as rotation degrees rather than pixel offsets.

As I said, I believe the use case of a rotation calls in the use of
double, exactly as it happens for other rotation APIs in the codebase.
Secondly I am against exporting the data as fixed point since that
would be burden to the end user and would tie this API to the google
specification too much. Finally I don't see what is wrong about these
fields being platform-specific, the whole structure is bound to be
platform specific, and the API mandates that a structure is used all
the time.
-- 
Vittorio