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Temporal fragments of media with time stamps

From: Bailer, Werner <werner.bailer@joanneum.at>
Date: Fri, 15 Jan 2010 16:56:07 +0100
To: "public-media-fragment@w3.org" <public-media-fragment@w3.org>
CC: Richard Wright-ARCHIVES <richard.wright@bbc.co.uk>
Message-ID: <CD9846F872C7874BB4E0FDF2A61EF09F4DADBBD3C2@RZJC1EX.jr1.local>
Dear all,

I had an email discussion with Richard Wright from the BBC, who brought up the following point: If media files have embedded time stamps (as it is possible e.g. in MPEG-2), temporal fragments should use them, instead of just using the offset from the start. This could for example make a difference when time stamps do not start at 0 at the beginning of the file or in case frames have been dropped during recording (i.e. the frame count from the start does not match any more).

The current specification is not clear, as it does not state whether it considers embedded time stamps if present:

- For the wall-clock time code I assume it does, otherwise it would have to get the date/time from some other source. 
- For the normalized play time I would expect to always specify a time offset relative to the start of the file.
- For the SMPTE time codes, it could consider time stamps if present.

Maybe you have already discussed that issue, then the specification should state how it is handled.

Best regards,
Werner
Received on Friday, 15 January 2010 15:58:11 GMT

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