feat(ABR): Allow some downscale when use restrictToElementSize or restrictToScreenSize

[avelad]

Closes: #5335
Closes: #5101

[shaka-bot]

Incremental code coverage: 28.21%

[joeyparrish]

I don't understand your logic here. On the previous two lines, we set maxHeight and maxWidth to resolution.height and resolution.width, so this condition is always true on this line. Right?

Overall, I would find this easier to review and verify with some comments in the code. Thanks!

[avelad]

I added a comment with an example for explanatory purposes.

[theodab]

I don't think this code would result in the behavior you explain in the comments, of looking for the smallest resolution that will "fit" the given max resolution. Given that it happens after maxWidth and maxHeight are re-defined, the inner if-condition is really testing resolution.height >= resolution.height && resolution.width >= resolution.width, which will only be false if the resolution is undefined, and thus it will cause the first resolution where EITHER width or height fits to be picked.

I think you probably just want to make the inner if-clause the outer check, and make it always break. Like...

if (resolution.height >= maxHeight && resolution.width >= maxWidth) {
  maxHeight = resolution.height;
  maxWidth = resolution.width;
  break;
}

[avelad]

Ok.. I changed it!

[joeyparrish]

This makes much more sense to me. Thanks!

Reviewed by Theodore

[siarheipashkevich]

@avelad hi, in the 4.5.0 version only low track selected for this manifest (there is no any changes when I changed my ethernet throttling):

<?xml version="1.0" encoding="UTF-8"?>
<MPD xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="urn:mpeg:dash:schema:mpd:2011" xmlns:cenc="urn:mpeg:cenc:2013" xsi:schemaLocation="urn:mpeg:dash:schema:mpd:2011 http://standards.iso.org/ittf/PubliclyAvailableStandards/MPEG-DASH_schema_files/DASH-MPD.xsd" type="static" minBufferTime="PT30S" profiles="urn:mpeg:dash:profile:isoff-main:2011" mediaPresentationDuration="PT5M13.792S">
  <Period start="PT0S" duration="PT5M13.792S" id="1">
    <AdaptationSet mimeType="video/mp4" frameRate="60000/1001" segmentAlignment="true" subsegmentAlignment="true" startWithSAP="1" subsegmentStartsWithSAP="1" bitstreamSwitching="false">
      <Representation id="1" width="1920" height="1080" bandwidth="8000000" codecs="avc1.64002a">
        <BaseURL>ducks_8000kbps.mp4</BaseURL>
        <SegmentBase indexRange="761-2684">
          <Initialization range="0-760"/>
        </SegmentBase>
      </Representation>
      <Representation id="2" width="1920" height="1080" bandwidth="4000000" codecs="avc1.64002a">
        <BaseURL>ducks_4000kbps.mp4</BaseURL>
        <SegmentBase indexRange="761-2684">
          <Initialization range="0-760"/>
        </SegmentBase>
      </Representation>
      <Representation id="3" width="1920" height="1080" bandwidth="1200000" codecs="avc1.64002a">
        <BaseURL>ducks_1200kbps.mp4</BaseURL>
        <SegmentBase indexRange="761-2684">
          <Initialization range="0-760"/>
        </SegmentBase>
      </Representation>
      <Representation id="4" width="1920" height="1080" bandwidth="400000" codecs="avc1.64002a">
        <BaseURL>ducks_400kbps.mp4</BaseURL>
        <SegmentBase indexRange="760-2683">
          <Initialization range="0-759"/>
        </SegmentBase>
      </Representation>
    </AdaptationSet>
    <AdaptationSet mimeType="audio/mp4" lang="und" segmentAlignment="0">
      <Representation id="5" bandwidth="96000" audioSamplingRate="48000" codecs="mp4a.40.2">
        <BaseURL>ducks_sd_2.mp4</BaseURL>
        <SegmentBase indexRange="658-2581">
          <Initialization range="0-657"/>
        </SegmentBase>
        <AudioChannelConfiguration schemeIdUri="urn:mpeg:dash:23003:3:audio_channel_configuration:2011" value="2"/>
      </Representation>
    </AdaptationSet>
  </Period>
</MPD>

But when I switched back to the 4.4.3 version the ABR working correctly for this manifest. What am I doing wrong?

FYI @theodab @joeyparrish