- From: David Singer <singer@apple.com>
- Date: Tue, 19 Jan 2010 16:48:06 +0900
- To: Davy Van Deursen <davy.vandeursen@ugent.be>
- Cc: "'Bailer, Werner'" <werner.bailer@joanneum.at>, public-media-fragment@w3.org, 'Richard Wright-ARCHIVES' <richard.wright@bbc.co.uk>, 'Jack Jansen' <Jack.Jansen@cwi.nl>
SMPTE time-codes are actually embedded in the media. They might be continuous in a media file, they might not be. For example, a fragment request for SMPTE 0h-10m-0s to 0h-20m-0s might appear to be a 10 minute clip starting 20 minutes in, but a) if the first time code in the file is in fact 0h-5m-0s, it's only 15 minutes into the clip (and indeed, TV time-codes typically treat 10h as the start time, I have no idea why) b) if there is a discontinuity in the time-codes such that 0h-15m-59s is followed by 0h-18m-0s, then it's only an 8 minute cli[p that's requested, in fact. On Jan 19, 2010, at 16:23 , Davy Van Deursen wrote: >> -----Original Message----- >> From: public-media-fragment-request@w3.org [mailto:public-media- >> fragment-request@w3.org] On Behalf Of David Singer >> Sent: maandag 18 januari 2010 2:38 >> To: Jack Jansen >> Cc: Davy Van Deursen; 'Bailer, Werner'; public-media-fragment@w3.org; >> 'Richard Wright-ARCHIVES' >> Subject: Re: Temporal fragments of media with time stamps >> >> >> On Jan 18, 2010, at 8:06 , Jack Jansen wrote: >> >>> >>> On 16 jan 2010, at 10:25, Davy Van Deursen wrote: >>>> >>>> Temporal fragments should indeed take into account embedded time >> stamps. >> >> 'may', I think, surely. It depends on whether the fragment time is >> expressed in NPT, or (say) SMPTE time-codes. NPT starts at 0; to >> resolve a fragment here, you're fine without inspecting the media. >> >> SMPTE time-codes, OTOH, need to be found. They might not even be >> continuous in the media. > > Hmm, what do you mean by 'need to be found'? Suppose an MP4 file starting > with an empty edit of 20s, followed by 40s video. What is the meaning of > t=npt:0,30 and t=smpte:00:00:00:00,00:00:30:00? IMO, they will both result > in an MP4 file starting with an empty edit of 20s, followed by 10s, no? > > Best regards, > > Davy > > -- > Davy Van Deursen > > Ghent University - IBBT > Department of Electronics and Information Systems - Multimedia Lab > URL: http://multimedialab.elis.ugent.be/dvdeurse > David Singer Multimedia and Software Standards, Apple Inc.
Received on Tuesday, 19 January 2010 07:48:41 UTC