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       HLS-26: Ability to override WRAP_POINT

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Issue Type: Sub-task 
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Issue Information
====================

Priority: Major					Status:      Open
Resolution:  Unresolved
Project: HLS Stream Creator (HLS)


Reported By: btasker					
Assigned To: btasker
Child of: HLS-25 - Additional flags/features to aid Low Latency Streaming  


Components: 
	- Linear Support 
	- CLI Options 


Targeted for fix in version: 
	- VNEXT

Labels: Linear, Segments, UltraLowLatency, 

Time Estimate: 180 minutes
Time Logged:   0 minutes


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Issue Description
==================

When creating a live stream, the point at which to start re-using segment names is
currently automatically calculated on line 343 and set as WRAP_POINT.

It only fires if the script has been told to limit the number of segments in the manifest
(by way of the -c flag)


-- BEGIN SNIPPET --

    if [ "$LIVE_SEGMENT_COUNT" -gt 0 ]
    then
	WRAP_POINT=$(($LIVE_SEGMENT_COUNT * 2)) # Wrap the segment numbering after 2 manifest
lengths - prevents disks from filling
	FFMPEG_ADDITIONAL+=" -segment_list_size $LIVE_SEGMENT_COUNT -segment_wrap $WRAP_POINT"
    fi

 -- END SNIPPET --

When WRAP_POINT is reached, segment filenames will reset, so we might see

- stream_00001.ts
- stream_00002.ts
- stream_00003.ts
- stream_00004.ts
- stream_00005.ts
- stream_00006.ts
- stream_00001.ts

For standard latency HLS streams this will generally be fine, however, for ultra-low
latency HLS streams we risk recycling names before the TTL on any downstream HTTP caches
has expired. Due to the very short segment length you risk increasing cache churn if the
TTL is lowered too much (and also meaning that if a player gets a bit behind, it may well
start skipping)

So, I'd like to add a flag (-w) that allows WRAP_POINT to be explicitly defined (and if it
isn't present, stick with the existing method of calculation), as well as perhaps having
the ability to tell it _never_ to wrap (though, as it stands, that would mean the older
segments are never removed from disk - that might be desirable if you're intending to
republish as VOD later though).

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Issue Relations
================
	
	- Line 343 (https://github.com/bentasker/HLS-Stream-Creator/blob/40dc4fca5c0364ea9887ebd3b70ac7be3b7aaf04/HLS-Stream-Creator.sh#L343)



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Activity
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2019-11-23 12:09:18              
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btasker added 'VNEXT' to Fix Version
	
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2019-11-23 12:09:18              
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btasker removed '1.0' from Fix Version