feat(dash): Improve DASH SegmentTemplate performance with on-demand segment references #5061
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avelad
added
type: enhancement
avelad
assigned littlespex, joeyparrish, avelad and theodab and unassigned littlespex, joeyparrish, avelad and theodab
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Incremental code coverage: 99.10% |
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I have tested on several TVs and the performance is better than before, I still have to do the code review. |
avelad
requested changes
Mar 21, 2023
joeyparrish
requested changes
Apr 19, 2023
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Overall, I'm very impressed with the performance improvements. Thank you so much for contributing! My main concern is that we take care of edge cases, especially around fitting segments to the period. |
joeyparrish
requested changes
Apr 25, 2023
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Please merge with main. I just fixed some test failures, and I'd like to see a clean test pass before I merge this. The PR looks good, though. Thanks! |
joeyparrish
changed the title
avelad
approved these changes
Apr 27, 2023
joeyparrish
approved these changes
Apr 29, 2023
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Background
This is a performance optimization intended to reduce the Video Start Time for DASH streams, both VOD and Live, by reducing the amount of processing done during manifest parse time. This is especially effective for long multi-period assets, assets with many variants, or on low end devices in general. I've provided some measurements showing the performance improvements at the conclusion of this PR.
Currently, during manifest parse time for a Segment Template, Shaka will loop through the entire timeline and create segment references for each timeline entry. For a long asset, or an asset with many tracks, this is a significant amount of processing.
Solution
I've created a new entity called the Timeline Segment Index that extends the SegmentIndex interface. The purpose of the Timeline Segment Index is to ingest a timeline during construction, and then use that information to build Segment References only on demand. This removes the need to parse the entire timeline and create all of the Segment References during parse time.
Results/Measurements
The effects of this change aren't quite as apparent on desktop web browsers, given their speed and power. This improvement really shines on lower end TVs on assets with a long timeline.