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

[Tim Nicholson]

On 27/03/12 18:50, Michael Niedermayer wrote:
> On Tue, Mar 27, 2012 at 12:09:54PM +0100, Tim Nicholson wrote:
>> On 27/03/12 07:47, Tim Nicholson wrote:
>>> On 26/03/12 23:55, Michael Niedermayer wrote:
>>>> On Mon, Mar 26, 2012 at 05:37:47PM +0100, Tim Nicholson wrote:
>>>>> Based upon some recent queries on ffmpeg-user, and my own experience, a little
>>>>> clarification of the documentation should help users in this area.
[..]
> 
> applied
> 

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.

Also unlike other cases -1 (auto) is not the default.

For consistency should scale be modified to conform to the norm?

I don't know what implications this might have as an API change.

-- 
Tim