Re: TextTrack questions

On 01/15/2014 03:02 PM, Aaron Colwell wrote:
> In the case of in-band tracks it is not clear what should be done
> because seeking back to an earlier portion of the clip would cause the
> file format parser to parse the cue data again and potentially try to
> insert it again. If the original cue was modified, then the cue data
> in the file and the values in the existing TextTrackCue wouldn't match
> so simple duplicate detection would not work. 
>
> Is the UA expected to keep a unique internal id for each in-band
> TextTrackCue it creates so that it doesn't reinsert a cue that was
> inserted previously, but was modified?

As far as I know, the spec doesn't say how to handle this. In WebKit, we
check if a cue already exists before adding it, so if we seek back and
see a cue with exactly the same startTime, endTime and text as an
existing cue, then we don't add it again.

Keeping track of cues by ID would be nice, but WebVTT cues don't
necessarily have ID's (and as far as I know, CEA-708 cues don't either).

Received on Thursday, 16 January 2014 18:19:30 UTC