[[ECMASCRIPT]] is unable to accurately represent numeric values greater than 253 (9007199254740991) using built-in types. Therefore, interoperable services cannot use such values.
All timescales are start times used in a DASH presentations SHALL be sufficiently small that no timecode value exceeding 253 will be encountered, even during the publishing of long-lasting live services.
Note: This may require the use of 64-bit fields, although the values must still be limited to under 253.
The issue does not arise with the common 90 KHz [=timescale=]. Counting time since the Unix epoch until 11 November 2019 we get 141721093260000 which is well within the allowed range of values.
Another common timescale is 10000000 (10 million [=timescale units=] per second) often used by Smooth Streaming. Counting time since the Unix epoch until 11 November 2019 we get 15746788140000000 which does exceed the critical value and will result in broken playback on many clients! To correct such an error, use a smaller timescale or a [=MPD timeline=] zero point that is not so far in the past.
All units expressed in [=MPD=] fields of datatype xs:duration SHALL be treated as fixed size:
- 60S = 1M (minute)
- 60M = 1H
- 24H = 1D
- 30D = 1M (month)
- 12M = 1Y
[=MPD=] fields having datatype xs:duration SHALL NOT use the year and month units and SHOULD be expressed as a count of seconds, without using any of the larger units.