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45 lines
1.9 KiB
45 lines
1.9 KiB
4 years ago
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# Adaptive Switching Behavior
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The HLS tech tries to ensure the highest-quality viewing experience
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possible, given the available bandwidth and encodings. This doesn't
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always mean using the highest-bitrate rendition available-- if the player
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is 300px by 150px, it would be a big waste of bandwidth to download a 4k
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stream. By default, the player attempts to load the highest-bitrate
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variant that is less than the most recently detected segment bandwidth,
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with one condition: if there are multiple variants with dimensions greater
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than the current player size, it will only switch up one size greater
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than the current player size.
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If you're the visual type, the whole process is illustrated
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below. Whenever a new segment is downloaded, we calculate the download
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bitrate based on the size of the segment and the time it took to
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download:
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First, we filter out all the renditions that have a higher bitrate
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than the new measurement:
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Then we get rid of any renditions that are bigger than the current
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player dimensions:
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We don't want to signficant quality drop just because your player is
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one pixel too small, so we add back in the next highest
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resolution. The highest bitrate rendition that remains is the one that
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gets used:
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If it turns out no rendition is acceptable based on the filtering
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described above, the first encoding listed in the master playlist will
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be used.
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If you'd like your player to use a different set of priorities, it's
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possible to completely replace the rendition selection logic. For
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instance, you could always choose the most appropriate rendition by
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resolution, even though this might mean more stalls during playback.
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See the documentation on `player.hls.selectPlaylist` for more details.
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