SegmentBase calculate segment count in accurate.

[zgzong]

When play or download a number-based VoD stream, player report the last segment is missing.

The stream information:
mediaPresentationDuration="PT2931.820S"

• ExoPlayer version number
  2.13.1

• Android version
  all os version

• Android device
  Samsung tablet SMP610

SegmentBase.java
public int getSegmentCount(long periodDurationUs) ... long durationUs = (duration * C.MICROS_PER_SECOND) / timescale; return (int) Util.ceilDivide(periodDurationUs, durationUs);

long durationUs = (179989 * 1000000) / 90000 = (long) 1,999,877.7777777777777777777777778 = 1999877
Util.ceilDivide(periodDurationUs, durationUs) = Util.ceilDivide( 2931820000 / 1999877) = 1467

Actually:
Based on https://dashif-documents.azurewebsites.net//DASH-IF-IOP/pull/210/DASH-IF-IOP.html#timing-addressing-simple-to-explicit
SegmentCount = Ceil(AsSeconds(Period@duration) / ( SegmentTemplate@duration / SegmentTemplate@timescale))
= Ceil ( 2931.820 / (179989 / 90000) ) = 1466.

[ojw28]

Thanks for reporting this. The problem with:

long durationUs = (duration * C.MICROS_PER_SECOND) / timescale;
return (int) Util.ceilDivide(periodDurationUs, durationUs);

is that durationUs is rounded down to the nearest microsecond. We can avoid any loss of precision by doing the calculation like this instead:

return (int) Util.ceilDivide(periodDurationUs * timescale, duration * C.MICROS_PER_SECOND);

[zgzong]

@ojw28 Thanks for your confirmation. The proposal works as ceilDivide will truncate the result only keep the integer part.

[ojw28]

We are a little concerned about the possibility of overflow of periodDurationUs * timescale, so will give this a bit more thought before submitting a fix.