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Re: Media Fragments in Opera

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Thu, 21 Oct 2010 10:48:53 +1100
Message-ID: <AANLkTikm8iCS_JBNeV+qD9itjp72jJQGAuAZyb2h3Kn1@mail.gmail.com>
To: Chris Double <cdouble@mozilla.com>
Cc: public-media-fragment@w3.org
On Thu, Oct 21, 2010 at 10:39 AM, Silvia Pfeiffer
<silviapfeiffer1@gmail.com> wrote:
> On Thu, Oct 21, 2010 at 10:32 AM, Chris Double <cdouble@mozilla.com> wrote:
>> On Thu, Oct 21, 2010 at 12:24 PM, Silvia Pfeiffer
>> <silviapfeiffer1@gmail.com> wrote:
>>>> How do you convert SMPTE to ms when you don't know the framerate? WebM
>>>> doesn't provide that information.
>>>
>>> How do you know at what speed to display WebM files if you don't have
>>> a framerate? I'm confused...
>>
>> We use the timestamps on the frame to know when that frame needs to be
>> displayed.
>
> Oh, so it's possible to have a non-fixed framerate in WebM? Hmm...
> Silvia.
>

It seems to me, looking at
http://groups.google.com/a/webmproject.org/group/webm-discuss/browse_thread/thread/2f0120b464b536c1/e7e1003f1be4c4fa?lnk=st&q=smpte#e7e1003f1be4c4fa
, one could use the TimecodeScale to calculate the conversion. Since
SMPTE is just a marker, it doesn't actually matter what frame rate the
video is encoded in. You can convert the SMPTE time marker to an
actual ms time and back only depending on what frame rate SMPTE you
pick. The actual frames available don't matter since SMPTE on digital
files isn't actually properly counting frames. This is why I call it a
marker and not a counter.

Silvia.
Received on Wednesday, 20 October 2010 23:49:46 UTC

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