[FFmpeg-devel] [PATCH] avutil/parseutils: only accept full us duration, do not accept mss duration

[Hendrik Leppkes]

On Thu, Mar 8, 2018 at 9:47 AM, Tobias Rapp <t.rapp at noa-archive.com> wrote:
> On 08.03.2018 00:14, Hendrik Leppkes wrote:
>>
>> On Thu, Mar 8, 2018 at 12:05 AM, Aurelien Jacobs <aurel at gnuage.org> wrote:
>>>
>>> On Wed, Mar 07, 2018 at 11:45:03PM +0100, Marton Balint wrote:
>>>>
>>>>
>>>>
>>>> On Wed, 7 Mar 2018, Aurelien Jacobs wrote:
>>>>
>>>>> On Tue, Mar 06, 2018 at 01:02:48AM +0100, Marton Balint wrote:
>>>>>>
>>>>>> Accepting 'u' suffix for a time specification is neither intuitive nor
>>>>>> consistent (now that we don't accept m).
>>>>>
>>>>>
>>>>> The 'm' SI prefix is still accepted in various time options, and the
>>>>> 'u'
>>>>> prefix is still accepted in those options even after your patch, so you
>>>>> can't really argue that this patch improve consistency.
>>>>> (eg. -black_min_duration 5ms is still accepted).
>>>>> So this will surprise nobody that I don't like this patch.
>>>>
>>>>
>>>> This really is a cursed topic, I am not sure I follow, after the patch:
>>>>
>>>> 5ms is accepted
>>>> 5us is accepted
>>>> 5m is not accepted
>>>> 5u is not accepted
>>>
>>>
>>> That is only for AV_OPT_TYPE_DURATION.
>>> All other numeric options type still accept SI prefix without unit.
>>> This include various time options such as black_min_duration.
>>> So after the patch, for black_min_duration:
>>>
>>> 5m is accepted
>>> 5u is accepted
>>>
>>
>> Because those use AV_OPT_TYPE_DOUBLE, a generic type without any
>> possiblity of a unit.
>> Ideally those should all be transitioned to AV_OPT_TYPE_DURATION if
>> they refer to a time for consistency, and not the actual time-type
>> bend to reflect some generic type. Why would we have the duration type
>> if its just a copy of the double type anyway?
>
>
> As a user with technical background I find it logical that
> AV_OPT_TYPE_DURATION is a superset of AV_OPT_TYPE_DOUBLE. Any
> double-formatted string is treated as a value in seconds. Additionally
> AV_OPT_TYPE_DURATION accepts HH:MM:SS formatted strings.
>
> So I think Aurelien has a point here: Why should we enforce a unit suffix
> for AV_OPT_TYPE_DURATION and loose the superset property?
>

Because something like "3m" for a time property is ambigious and
confusing. I would personally never expect that to mean "3ms", and as
this thread has shown here, I would not be alone with that
interpretation.

- Hendrik