[FIXED] Parse media presentation time from dash manifest java?

Issue

In a streaming video dash manifest we receive the media presentation time as PT461486H44M42.24S. This is basically a timestamp for the media segment to be loaded. Sample will be

  <Period id="C 2022-08-26 08-45-41" start="PT461486H44M42.24S">

I want to know what is this time format? And how can I convert it to long milliseconds. I checked the [SimpleDateFormat] SDF but it doesn't matches.

Solution

Your String seems to represent a duration in ISO-8601 format.

You can use java.time.Duration.parse in order to create a Duration which may give you information about specific unit. Since a duration is an amount of time in contrast to epoch millis, you should not convert Duration.toMillis() to any date or datetime. They are basically totally different.

Here's an example usage of a Duration derived from your String:

public static void main(String[] args) {
    // your example String
    String durStr = "PT461486H44M42.24S";
    // parse it to a Duration
    Duration duration = Duration.parse(durStr);
    // create a result message from the units of a Duration
    String durMsg = String.format("%d milliseconds are %d days, %d hours, %d minutes, %d seconds and %d milliseconds",
                                duration.toMillis(),
                                duration.toDays(),
                                duration.toHoursPart(), 
                                duration.toMinutesPart(), 
                                duration.toSecondsPart(), 
                                duration.toMillisPart());
    // print the result message
    System.out.println(durMsg);
}

Output:

1661352282240 milliseconds are 19228 days, 14 hours, 44 minutes, 42 seconds and 240 milliseconds

---

If you suspect the result of duration.toMillis() not to be the length of the video but , for example, the creation timestamp (in epoch millis) or the age in millis, don't use the outdated API (Date, SimpleDateFormat and so on) but use java.time. You can use those millis to create an Instant which you can then use to create a ZonedDateTime of OffsetDateTime:

// create a Temporal using an Instant and a fixed time zone (UTC here)
ZonedDateTime zdt = ZonedDateTime.ofInstant(
                        // create an Instant from the millis
                        Instant.ofEpochMilli(duration.toMillis()),
                        // and apply a fixed time zone
                        ZoneOffset.UTC
                    );
// print the result
System.out.println(zdt);

Output:

2022-08-24T14:44:42.240Z

---

Different idea:

You can subtract the parsed Duration from a current moment in time, which – under circumstances – may give you the moment in time of the first media presentation (like when it was released):

Instant instant = Instant.now().minus(duration);
ZonedDateTime zdt = ZonedDateTime.ofInstant(
                        // create an Instant from the millis
                        Instant.ofEpochMilli(duration.toMillis()),
                        // and apply a fixed time zone
                        ZoneOffset.UTC
                    );
System.out.println(zdt);

This just output the following:

1970-01-01T21:37:52.460090Z

This approach is just an idea and it heavily depends on the duration between receiving the media presentation time (your String) and the calculation involving Instant.now(), which should ideally be the same moment in time in order to get the (most) correct time of the media presentation.

Answered By - deHaar
Answer Checked By - Candace Johnson (JavaFixing Volunteer)