[FFmpeg-devel] MXF D10 regression tests

[Måns Rullgård]

Michael Niedermayer <michaelni at gmx.at> writes:

> On Wed, Mar 18, 2009 at 04:04:49PM +0100, Reimar D?ffinger wrote:
>> On Wed, Mar 18, 2009 at 03:40:52PM +0100, Michael Niedermayer wrote:
>> > iam not asking for all of it to be taken into account but rather that
>> > there is some framework in which such things can be filled in where
>> > they are needed.
>> > (we also have avcodec_align_dimensions())
>> 
>> Well, you are the maintainer, I leave it to you to come up with a
>> solution. At least it should be clear enough what exactly is the issue
>> and can be fixed without access to a PPC machine.
>> 
>> > currently STRIDE_ALIGN is 8 for x86* and that works out exactly
>> > because 420 and the linesize relations gurantee 16 byte alignment
>> > for luma.
>> 
>> I want to make completely clear: there is nothing in the code that
>> guarantees any "linesize relations", it is pure luck it works, and the
>> only reason is that the width is required to be a multiple of 16 and
>> STRIDE_ALIGN << chroma_x_shift divides (more precisely is equal to)
>> this on x86.
>> 
>> > if 444 is ever added it will need some special handling like svq1 does,
>> > also other archs than x86 set STRIDE_ALIGN to 16 while they possibly
>> > like x86 really just mean 16 for luma ...
>> 
>> Since (probably) none of that is documented that won't be fixed anytime
>> soon, at least not by someone who does not know the asm by heart already.
>
> there was a single line of doc until r12178
> the code surrounding has changed several times prior
>
> and i simply do not remember which asm or how many if any need this
> linesize relation.
>
> it is possible that some of the code expecting the linesize relation was
> fixed in the distant past to use uvlinesize/stride
>
> what should be done is
> * identify and document which code exactly needs this relation (your patch
>   is a start for this)
> * find what speed effect it has to fix that code
> * depending on the possibility to fix the code without speed regressions
>   document which buffers require the relation and fix the code used to
>   allocate them
> * fix STRIDE_ALIGN for each arch (really a job for the maintainers of that
>   archs)

Do we have to do all of that before we can fix the encoding on PPC and
ARM?

-- 
M?ns Rullg?rd
mans at mansr.com