Re: [AVT] Carrying SMPTE TimeCode in RTP

On 2 Mar 2006, at 00:42, Dave Singer wrote:
> Answering my own email here, I'm assuming that the answer is yes to  
> the 2nd question.
>
> The extra bits in an 8-byte SMPTE time-code can be used to
> a) maintain the polarity of the code (numbers of 1s and 0s)
> b) indicate the relationship of the codes to color fields
> c) indicate whether it's drop-frame coding
> d) and then do one of
>    i) carry 4 characters more
>    ii) carry a date and time-zone indication (SMPTE 309M)
>    iii) carry some general SMPTE 262M data (control codes, text,  
> production info etc.)
>
> I don't believe we need color and polarity handling in RTP.
> We have drop-frame in the signalling.
>
> If we want to carry something as slowly-changing as a date or as  
> unchanging as a time-zone, I on't believe that embedding it here is  
> right.  Certainly thought should be applied before blindly applying  
> it.  If a date is needed, it's not needed inline;  at most it would  
> be in RTCP, and then I would argue for a new RTCP packet type to  
> carry it.
>
> The other two possibilities are 'general meta-data' and should not  
> be sub-embedded in a time-code, in RTP, but elevated and properly  
> labelled at the stream level.
>
> So, my answer is no, we do not need the full 8-byte SMPTE time-code.

Seems reasonable.

Colin

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