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Re: Aligning NPT syntax with RTSP

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Fri, 29 Jan 2010 14:15:13 +1100
Message-ID: <2c0e02831001281915v16463cd3s4a127adacedbfdb4@mail.gmail.com>
To: Philip Jägenstedt <philipj@opera.com>
Cc: public-media-fragment@w3.org
I'd go with http://www.w3.org/TR/NOTE-datetime and prescribe two digits each.
Maybe link to ISO 8601, this TR and the RFC together and say that this
is what we chose?
Or alternatively if there is something in HTML5, just link to that?

Cheers,
Silvia.

On Fri, Jan 29, 2010 at 11:53 AM, Philip Jägenstedt <philipj@opera.com> wrote:
> On Fri, 29 Jan 2010 01:21:48 +0100, Silvia Pfeiffer
> <silviapfeiffer1@gmail.com> wrote:
>
>> On Fri, Jan 29, 2010 at 10:05 AM, Philip Jägenstedt <philipj@opera.com>
>> wrote:
>>>
>>> On Wed, 27 Jan 2010 23:28:05 +0100, Silvia Pfeiffer
>>> <silviapfeiffer1@gmail.com> wrote:
>>>
>>>> On Wed, Jan 27, 2010 at 11:45 PM, Philip Jägenstedt <philipj@opera.com>
>>>> wrote:
>>>>>
>>>>> On Wed, 27 Jan 2010 13:32:11 +0100, Silvia Pfeiffer
>>>>> <silviapfeiffer1@gmail.com> wrote:
>>>>>
>>>>>> On Wed, Jan 27, 2010 at 10:33 PM, Philip Jägenstedt
>>>>>> <philipj@opera.com>
>>>>>> wrote:
>>>>>>>
>>>>>>> On Wed, 27 Jan 2010 12:23:25 +0100, Silvia Pfeiffer
>>>>>>> <silviapfeiffer1@gmail.com> wrote:
>>>>>>>
>>>>>>>> On Wed, Jan 27, 2010 at 10:09 PM, Philip Jägenstedt
>>>>>>>> <philipj@opera.com>
>>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> http://www.w3.org/2008/WebVideo/Fragments/WD-media-fragments-spec/#npttime
>>>>>>>>>
>>>>>>>>> This is what I mentioned in the teleconf. As it is, '0.' would not
>>>>>>>>> be
>>>>>>>>> a
>>>>>>>>> valid production of npttime but it is a valid production of npt-sec
>>>>>>>>> from
>>>>>>>>> RTSP [1]. The same is true of '00:00:00.'. The difference is in
>>>>>>>>> digits
>>>>>>>>> after
>>>>>>>>> the decimal point.
>>>>>>>>
>>>>>>>> We currently have:
>>>>>>>>
>>>>>>>> npttime    ::=          ( 1*DIGIT [ "." 1*DIGIT ] [ timeunit ] ) |
>>>>>>>>                     ( 1*DIGIT ":" 2DIGIT ":" 2DIGIT [ "." 1*DIGIT] )
>>>>>>>>
>>>>>>>> which I think you are proposing to change to
>>>>>>>>
>>>>>>>> npttime    ::=          ( 1*DIGIT [ "." *DIGIT ] [ timeunit ] ) |
>>>>>>>>                     ( 1*DIGIT ":" 2DIGIT ":" 2DIGIT [ "." *DIGIT] )
>>>>>>>>
>>>>>>>> Correct?
>>>>>>>
>>>>>>> To be precise, I'm suggesting referring to the definition in RFC2326,
>>>>>>> noy
>>>>>>> copying it. The effect is the same of course.
>>>>>>
>>>>>> Could do ...  otoh if the RTP spec changes this, we are not
>>>>>> dependent... and it's really short.
>>>>>
>>>>> RFCs can never change, but I have no objections to copying as long as
>>>>> there
>>>>> is a (normative?) reference to RFC2326 for readers to follow.
>>>>
>>>> Yeah, that's right. I guess the only reason then is not to have to go
>>>> and read another document.
>>>> I'm happy to add a normative reference to RFC2326 and still leaven the
>>>> two-liner in there.
>>>
>>> I tried making the edit and it turns out RFC2326 is a bit quirky on the
>>> HHMMSS format:
>>>
>>>  npt-hhmmss   =   npt-hh ":" npt-mm ":" npt-ss [ "." *DIGIT ]
>>>  npt-hh       =   1*DIGIT     ; any positive number
>>>  npt-mm       =   1*2DIGIT    ; 0-59
>>>  npt-ss       =   1*2DIGIT    ; 0-59
>>>
>>> It allows 1-digit minute or second, which we currently do not. Do we
>>> really
>>> want this?
>>
>> I think you may be misreading this. npt-mm and npt-ss say "use one
>> 2DIGIT", i.e. there are two digits always, IMO.
>
> Following the references back to ABNF in
> http://www.ietf.org/rfc/rfc2068.txt:
>
> *rule
>     The character "*" preceding an element indicates repetition. The
>     full form is "<n>*<m>element" indicating at least <n> and at most
>     <m> occurrences of element. Default values are 0 and infinity so
>     that "*(element)" allows any number, including zero; "1*element"
>     requires at least one; and "1*2element" allows one or two.
>
> Also, the RTSP spec proclaims that "The syntax conforms to ISO 8601." I'm
> unable to figure out if ISO 8601 allows single-digit hours and minutes or
> not. Is anyone familar with RTSP so that they can check if implementations
> actually support this, or if it might just be a typo?
>
> --
> Philip Jägenstedt
> Core Developer
> Opera Software
>
Received on Friday, 29 January 2010 03:16:06 GMT

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