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Description
Earlier today, Apple released a new strobing mitigation media accessibility accommodation in tvOS 16.4, iOS 16.4, and macOS 13.3, called "Dim Flashing Lights." (Additional links below)
Prior to this, the typical behavior with flashing media was that a viewer was warned once before before a video played. Even in a feature length film, there was no indication of when the flashing may occur, and no information about the intensity or type of strobing.
On Apple devices, we can now adjust for some strobing/flashing in real time with onboard hardware and software, but as Apple's TV+ content is viewable on many other platforms, we'd also like to be able to do this on non-Apple hardware.
We think proposing a time-coded metadata track of flash level as an accessibility standard makes sense, as other platforms may wish to adopt their own form of strobing mitigation or warnings.
So we'd like the WG to consider using a WebVTT metadata track to allow streaming services and content owners to denote areas of flashing in video time codes, similar to a caption track.
Minimum proposal
WEBVTT
1
00:00:10.123 --> 00:00:15.432
{
type: "video.strobing.general-flash",
level: "75"
}
2
00:00:47.462 --> 00:01:04.028
{
type: "video.strobing.general-flash",
level: "100"
}
We're not particular to the proposed key names or value formats, but the type value above aligns with an expected update to HLS, and accounts for future expansion into other common strobing patterns such as red-flash
and spatial-pattern
.
Variant proposal that accounts for algorithm and version
Ideally, in order to ensure all content publishers, software developers, and users have the same understanding and representation of the level, the VTT cue format could account for different, documented algorithms and versions for each of those.
Apple published a new general flash algorithm (PDF) for use alongside the related native platform API or for use in other contexts.
In order to differentiate from other flash pattern algorithms in WebVTT (Harding, for example), the metadata cue could contain a published URI (or registered name?), as well as a version number. For example:
WEBVTT
1
00:00:10.123 --> 00:00:15.432
{
type: "video.strobing.general-flash",
level: "75",
test-uri: "https://developer.apple.com/accessibilty/...",
test-version: "1.0"
}
2
00:00:47.462 --> 00:01:04.028
{
type: "video.strobing.general-flash",
level: "100",
test-uri: "https://developer.apple.com/accessibilty/...",
test-version: "1.0"
}
We're not particular to the proposed key names or values, and look forward to discussing further with the Working Group.
Prerequisite:
I have filed another issue we believe is important to consider alongside this one.