When describing closed captions renditions through HLS master playlists, should a properly formed playlist with closed captions contain one closed caption rendition with the DEFAULT=YES attribute? I searched the HLS RFC and section 4.3.4.1 on EXT-X-MEDIA mentions that no more than one should contain the DEFAULT=YES attribute. I was hoping to find recommendations around whether with one or more EXT-X-MEDIA renditions in the same group, if it is required that one of them contain DEFAULT=YES.
The media player I am using does not display closed captions if one of the closed captions renditions does not contain the DEFAULT=YES attribute and I am wondering if that is an issue with the player or an issue with a malformed HLS playlist. Note the lack of a DEFAULT=YES attribute in the example playlist below. Should this still be considered a valid playlist?
#EXTM3U
#EXT-X-VERSION:3
#EXT-X-INDEPENDENT-SEGMENTS
#EXT-X-MEDIA:TYPE=CLOSED-CAPTIONS,GROUP-ID="CC",LANGUAGE="eng",NAME="English",INSTREAM-ID="CC1"
#EXT-X-STREAM-INF:BANDWIDTH=2103200,AVERAGE-BANDWIDTH=2305600,CODECS="avc1.640029,mp4a.40.2",RESOLUTION=960x540,FRAME-RATE=30.000,CLOSED-CAPTIONS="CC"
https://the.link.to.my.stream
#EXT-X-STREAM-INF:BANDWIDTH=804760,AVERAGE-BANDWIDTH=875600,CODECS="avc1.640029,mp4a.40.2",RESOLUTION=640x360,FRAME-RATE=30.000,CLOSED-CAPTIONS="CC"
https://the.link.to.my.stream
#EXT-X-STREAM-INF:BANDWIDTH=1304160,AVERAGE-BANDWIDTH=1425600,CODECS="avc1.640029,mp4a.40.2",RESOLUTION=768x432,FRAME-RATE=30.000,CLOSED-CAPTIONS="CC"
https://the.link.to.my.stream
#EXT-X-STREAM-INF:BANDWIDTH=505120,AVERAGE-BANDWIDTH=545600,CODECS="avc1.640029,mp4a.40.2",RESOLUTION=480x270,FRAME-RATE=30.000,CLOSED-CAPTIONS="CC"
https://the.link.to.my.stream
#EXT-X-STREAM-INF:BANDWIDTH=3102000,AVERAGE-BANDWIDTH=3405600,CODECS="avc1.640029,mp4a.40.2",RESOLUTION=1280x720,FRAME-RATE=30.000,CLOSED-CAPTIONS="CC"
https://the.link.to.my.stream