[FFmpeg-devel] [PATCH] Clarifying the use of the scale filter interlace option

[Tim Nicholson]

On 29/03/12 20:33, Michael Niedermayer wrote:
> On Thu, Mar 29, 2012 at 08:49:38AM +0100, Tim Nicholson wrote:
[...]
>> Whilst investigating this it occurred to me that this filter behaves
>> differently by default to other filters and options.
>>
>> Commonly values of 1|0|-1 are used, with -1 meaning "auto" in whatever
>> way that applies to the relevant filter/option, with the other values
>> forcing a particular behaviour between a choice of 2. -1 is also
>> commonly the default value.
>>
>> For example the following all use -1 as the default if not specified:-
>> rawvideo top
>> -mixing_level number
>> -channel_coupling boolean
>> -cpl_start_band number
>> amovie|movie stream_index
>> yadif
>> cellauto|life random_seed
>>
>> scale however only has 1|-1 with 0 having no defined meaning, although
>> the logic dictates that since it is neither of the others it is an
>> invalid choice and therefore ignored.
> 
> 0 should mean progressive

Sorry badly worded :( . The code only checks for "interl=1" or
"interl=-1" to consider if interlaced scaling should be used (forced or
auto selected), any other value, including 0, is ignored, which leads to
the default of progressive handling.

> 
> 
>>
>> Also unlike other cases -1 (auto) is not the default.
> 
> this could be changed if it works better overall

It looks a fairly simple logic change, and I am happy to have a go at a
patch to bring it into line with other features, but I didn't know if
changing the default might have other repercussions. It should be safe
in auto.



-- 
Tim