[MPEG-OTSPEC] Updates to specification

[David Singer]

> On Aug 13, 2020, at 15:08 , John Hudson <john at tiro.ca> wrote:
> 
> On 13082020 12:07 pm, Levantovsky, Vladimir wrote:
>> I’d argue that for as long as we collectively treat this work as a single entity and discuss everything out in the open, with all interested parties being able to freely join the discussion – the _formal_ agreement isn’t necessary (I am not even sure there can be such a thing with ISO having full rights to make changes to their document). We, as a community have vested interest in maintaining the integrity of the technology, and developing it further in a way that facilitates widespread adoption and implementations.
> Vlad, does ISO/MPEG have any kind of implementation requirement similar to, say, the W3C independent implementations requirement? Is it possible to institute one?

Not overall at ISO, but the codec groups at MPEG certainly insist on reduction to practice in the reference software, and that there should also be conformance files that contain/use the feature. That enables verification and testing. 

> 
> One of the things that has concerned me about both the OT and OFF is that they have sometimes been what I would class as speculative specifications, and have numerous features that are formally part of the format but have never been implemented (Peter just reminded us of one). In recent years, there has been some improvement in this regard, e.g. the implementation many aspects of OT variations before the 1.8 spec was published, but so far as I am aware there is no requirement for implementation built into the processes, and nothing like a public draft stage such as CSS has.

In the systems groups at MPEG we have amended out of specs features for which no-one could provide EITHER reference software or conformance files; we figure if no-one can produce a single file that uses the feature, after repeated asks, it’s not in use.

> 
> JH
> 
> -- 
> 
> John Hudson
> Tiro Typeworks Ltd    
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David Singer
Manager, Software Standards, Apple Inc.