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Re: [Bug 26526] Fix aspect ratio constraint

From: Gili T. <cowwoc@bbs.darktech.org>
Date: Thu, 14 Aug 2014 11:45:38 -0400
Message-ID: <CAPeFFaC67VbxjB-D1phN5k-S+Q2bh7NAWv7y4dxytS1P3zbh5w@mail.gmail.com>
To: Harald Alvestrand <harald@alvestrand.no>, public-media-capture@w3.org
Hi Harald,

Can you please explain how an epsilon of 1/1000 equates to one pixel in HD?

What able future proofing? What happens when we want 4k resolution in the
future?

Thanks,
Gili
On Aug 13, 2014 1:11 PM, "Harald Alvestrand" <harald@alvestrand.no> wrote:

>  On 08/13/2014 12:11 PM, Gili T. wrote:
>
> And I'll repeat that different ratios will need different epsilons.
> Epsilons imply inaccuracy and there is no one number that will work for
> every use case. Why not just go with "numerator/denominator", parse it to
> two integers and compare with 100% accuracy?
>
>
> Did you intend for this to go to me only?
>
> 1/1000 is one pixel in HD. We don't need more precision.
>
>
>  Gili
> On Aug 13, 2014 8:50 AM, "Harald Alvestrand" <harald@alvestrand.no> wrote:
>
>> On 08/12/2014 06:17 PM, Jan-Ivar Bruaroey wrote:
>>
>>> On 8/11/14 6:17 PM, Martin Thomson wrote:
>>>
>>>> On 11 August 2014 14:34, Jan-Ivar Bruaroey <jib@mozilla.com> wrote:
>>>>
>>>>> Actually, the spec already says: "The exact aspect ratio (width in
>>>>> pixels
>>>>> divided by height in pixels), represented as a double rounded to the
>>>>> tenth
>>>>> decimal place" [1]
>>>>>
>>>>> So we effectively have our epsilon already: .0000000001
>>>>>
>>>>> So no action required it seems.
>>>>>
>>>> Oh, that's good, there's an epsilon; but it's bad.  1.777777778 isn't
>>>> the same as 16/9 based on that.  Nor is 1.7777777777.  Add a single
>>>> digit to either and it would match.  I may have counted wrong. I'm
>>>> sure that others will too.
>>>>
>>>
>>> Feel free to propose a different epsilon I suppose.
>>>
>>> I presume this would have nothing to do with inaccuracies inherent in
>>> floating-point math then (or we could have picked an epsilon much closer to
>>> everyone's worst machine epsilon), but instead from a desire to accommodate
>>> people handwriting rounded decimal numbers for aspect. Just so we're clear
>>> on the properties we seek.
>>>
>>
>> I'll repeat my suggestion of an epsilon of 1/1000.
>>
>>
>>> .: Jan-Ivar :.
>>>
>>>
>>>
>>
>>
>
Received on Thursday, 14 August 2014 15:46:06 UTC

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