1. Time Format for a New Label
Why PTP?

2. Time Labels Have Multiple Uses
No one label format is optimal for all use cases
No one time format is optimal for all use cases
No one epoch is optimal for all use cases
The design essential is that the chosen format support all known use cases (via use-case applications where necessary)
Where there are multiple use cases, good engineering requires that the design be as universal as possible, and not “build in” assumptions about specific use cases.
The label design should be independent of any specific transport

3. The “Digital Birth Certificate”
Concept first advanced at Hollywood reach-out meeting in 2010
Comprises …
Time value
Source ID
Media-unit counter(s)
Conveys all essential information for captured content
It should be possible to add additional fields (such as SMPTE 12) as needed for later processes (post production, playout preparation, etc.)

4. Simplicity is a Virtue
Attempts to address specific user requirements and human-interface issues add complexity to the label, and may reduce its universality
Many listed requirements (such as Daily Jam) have local variations and parameters. These are best addressed by user applications
Calculation is inexpensive. A single time format such as PTP can easily be rendered in any required form such as HH:MM:SS:FF

5. PTP is the Natural Choice
As SMPTE experts have made very clear, conversion among time formats is complex, maybe even ambiguous, and difficult to solve in the general case
SMPTE has adopted PTP for 2059 and 2110 series documents
These, together with the time label are fundamental; SMPTE should NOT permit any complexity of time conversion across there Standards
Time-format conversion routines for application at the point of use already exist and are easy to implement

6. Some Objections to PTP
Needs to work for absolute and non-absolute time
Any non-absolute time may be derived from the media-unit count
EDLs etc. need to work in media units
Most edit systems define their own internal indexing; a media-unit count is provided in the proposed label
You don't have to constrain every time label to use the same time unit
That’s just another way of de-standardizing the label (creating multiple labels)
Program time does not depend on absolute acquisition time
Program time does not even need a label; it may be created from the required start time and a local media-unit count (just like striping)

7. Summary
The proposed Time Label, based on the “Digital Birth Certificate” definition, provides support for all known use cases, including variable frame rate, time lapse, etc. etc.
It is simple, but extensible, and is not compromised by assumptions about specific use cases
Use of PTP aligns with other core SMPTE Standards
SMPTE 12 was adopted in many industries; use of IEEE 1588 will encourage similar widespread acceptance of the new label
Conversion from PTP is well-documented and simple to implement