Typo in §3.9.5.2 about audio description

[TanguyPerson]

If I understand properly, "audio description" is a property of the audio channels, so

• If audio description are requested
  • all video Adaptation Sets that have an Accessibility descriptor (...)

should be

• If audio description are requested
  • all audio Adaptation Sets that have an Accessibility descriptor (...)

[haudiobe]

I believe the text is correct as audio descriptions are video that describe the spoken audio. Or is audio description an additional description added to audio to describe the video? If the latter then we need to change. More discussion necessary. There are other types of descriptions, so we should recheck the role scheme and the usage in DASH.

[TanguyPerson]

I am no expert on accessibility subjects and such types of media tracks. I was just relying on where the "description" role is mentioned.

In fact, looking deeper, I see several inconsistencies in the use of "description" role for Accessibility :

• for video, -- §3.9.5.2 lists "caption", "sign" and "description" roles (but not "subtitle") -- §3.9.4.5 lists "sign, "caption" and "subtitle" roles (but not "description') -- table 4 in §3.9.2 lists "sign" and "caption" roles (but not "subtitle" nor "description)
• for audio, -- §3.9.5.2 lists "enhanced-audio-intelligibility" role (but not "description") -- §3.9.4.6 lists "description" and "enhanced-audio-intelligibility" roles -- table 4 in §3.9.2 "description" and "enhanced-audio-intelligibility" roles
• for text tracks -- §3.9.5.2 lists "caption" role (but not "description" nor "caption" nor "sign") -- §3.9.4.7 lists "caption" and "description" roles (but not "sign") -- table 4 in §3.9.2 lists "caption" and "sign" roles (but not "description")

I am not sure interpret things correctly, but IMHO:

• "sign" is not a relevant value for the text tracks in table 4 of §3.9.2
• "description" is not a relevant value for the video tracks in §3.9.5.2 (at least does not apply to audio description)
• "description" is the value for the audio description mode of audio track, §3.9.5.2 should be updated
• "subtitle" should be an allowed value for video in table 4 of§ 3.9.2 (for "burned" subtitles)

[pmaness]

In DVB there are 3 audio features described to support certain special needs of viewers. In the preselection descriptor these are called:

1. audio_description : In ATSC this is called Descriptive Video Service. This is an audio track that has a narration describing what is happening in the video. I think this was the inteded usage and would agree with the suggestion made by the OP.
2. spoken_subtitles: This is a narrator reading the subtitle track aloud (talking over the dialog?). If it is important, we should add a DASH role for this. (This may be the same as a dubbed language track? ATSC doesn't seem to define this, at least not in A/342-1).
3. dialog_enhancement: This feature is intended to improve dialog intelligibility for people with certain hearing impairments. (e.g. supressing loud background music so the dialog of the actors can be understood). ATSC also calls this dialog enhancement.

I don't know if we can, or should, attempt to reconcile these terms, but we should at least define the terms we are using so it's clear.

[xavierlaffargue-radiocanada-cbc]

Hi, some news about that?