Captions can't be turned on using Google Assistant

Version

Media3 main branch

More version details

I'm trying to achieve the same functionality on Android TV as it was possible using ExoPlayer and MediaSessionConnector.

Previously using MediaSessionConnector.CaptionCallback it was possible to enable subtitles using Google Assistant. I can't find any references to this with Media3. Is this feature supported with on-device integration, or am I missing something?

Note: From investigation we may be able to workaround this accessing (MediaSessionCompat) MediaSession#Impl, but this field is private, and accessing this might result in unwanted behaviours. Also MediaSessionLegacyStub says: "no-op" in onSetCaptioningEnabled implementation.

Used versions:
androidx.media3: v1.3.1
katniss: v7.10.20240225.1_cl.4
OS: A10, A11
androidx.media: v1.7.0 (for compat)

Devices that reproduce the issue

Android TV and STBs

Devices that do not reproduce the issue

No response

Reproducible in the demo app?

Yes

Reproduction steps

When the Playback is running, with mediaSession set up, use the following ADB command:
adb shell am start -a android.search.action.GLOBAL_SEARCH --es query 'enable\ captions'

Previously this invoked MediaSessionCompat#onSetCaptioningEnabled callback. (and still happening, but it's hidden)

Expected result

Callback should be accessible or exposed.

Actual result

Google Assistant says "Sorry, I can't do that on this app."

Media

https://devstreaming-cdn.apple.com/videos/streaming/examples/bipbop_16x9/bipbop_16x9_variant.m3u8

Bug Report

• You will email the zip file produced by adb bugreport to android-media-github@google.com after filing this issue.