[Hls-interest] rendition report clarification

[Scott Kellicker <[e-mail]>]

At least to me the spec is not clear about rendition-reports between audio
streams and video streams.  Looking at LLHLS streams produced by several
companies, I see different behavior.

To take an example.  If I have one audio group rendition and 3 video
renditions which point back to the audio group.  For example:

curl http://IP/playlist.m3u8
#EXTM3U
#EXT-X-VERSION:6
#EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="Audio",URI="audio1.m3u8"
#EXT-X-STREAM-INF:BANDWIDTH=3600000,CODECS="avc1.4d4c28,mp4a.40.2",RESOLUTION=1920x1080,AUDIO="Audio"
video1.m3u8
#EXT-X-STREAM-INF:BANDWIDTH=1400000,CODECS="avc1.4d4c1e,mp4a.40.2",RESOLUTION=540x360,AUDIO="Audio"
video2.m3u8
#EXT-X-STREAM-INF:BANDWIDTH=750000,CODECS="avc1.4d4c15,mp4a.40.2",RESOLUTION=320x240,AUDIO="Audio"
video3.m3u8

Q. When I return the m3u8 for one of the video renditions, should the
REND-REPORT contain the audio m3u8?

$ curl http://IP/video1.m3u8 |grep REND. ; should have all the audio RRs
when requesting video m3u8
#EXT-X-RENDITION-REPORT:URI="audio1=.m3u8",LAST-MSN=131,LAST-PART=1
#EXT-X-RENDITION-REPORT:URI="video2.m3u8",LAST-MSN=131,LAST-PART=1
#EXT-X-RENDITION-REPORT:URI="video3.m3u8",LAST-MSN=131,LAST-PART=1

Q. Conversely, when I return the rendition report for the audio rendition,
should it contain the 3 video rend report entries?

curl http://IP/audio1.m3u8 |grep REND.  ; should have all the video RRs
when requesting audio m3u8
#EXT-X-RENDITION-REPORT:URI="video1.m3u8",LAST-MSN=122,LAST-PART=1
#EXT-X-RENDITION-REPORT:URI="video2.m3u8",LAST-MSN=122,LAST-PART=1
#EXT-X-RENDITION-REPORT:URI="video3.m3u8",LAST-MSN=122,LAST-PART=1



mediastreamvalidator would seem to answer "yes" to both questions.
However, in my experience MSV is often wrong and can conflict with the
spec.  (And what ultimately matters is the spec AND what players expect)


Scott Kellicker
Blank Canvas Video LLC