We are developing a real-time subtitle translation accessibility app for a PS5 connected directly to a consumer LG OLED TV. The intended runtime setup is PS5 + TV only, without a capture card, external computer, root access, firmware modification or HDCP circumvention. We need a supported, permissioned way to obtain downscaled HDMI frames for OCR and display translated subtitles. No OCR/translation success is claimed.
TEST ENVIRONMENT
TV: OLED65C64LA; firmware: 43.21.79; SDK reported by ares-device: 11.2.0; board: O26_DVB_EU. Packaged web app v0.1.2 installed through official Developer Mode (prisoner), Chromium 132 WebAppManager. requiredACG is empty; no privileged capture services are called.
ACTUAL TV FINDINGS
- ext://hdmi:3 with source type service/webos-external shows moving PS5 content with DOM subtitle text on top, confirmed by the operator. We understand this path’s consumer-TV support is not established by public documentation.
- Transparent standard and experimental overlay windows did not preserve the native HDMI picture in our observed tests.
- Canvas drawImage(video) + getImageData returns transparent zero data.
- createImageBitmap(video): InvalidStateError, bitmap could not be allocated.
- VideoFrame from the external video has null format; allocationSize with RGBA fails with NotSupportedError.
- WebGL texture readback: framebuffer incomplete.
- A separate synthetic canvas control is readable through all four copy paths. This is not an HDMI or decoded-media control.
- The experimental texture attribute did not improve these results. Signage IDCAP APIs were not used.
- video.captureStream produces a track, but sampled content is black. Its reported 30 fps metadata is not treated as a gaming frame-rate measurement.
- getDisplayMedia({video:true,audio:false}), initiated by physical TV user interaction, returns AbortError: Invalid state. No LG system source-selection dialog was confirmed.
- The operator reported HDR preserved in the app-contained HDMI view. FPS could not be verified: Game Dashboard was unavailable and Game Optimizer was disabled while the app was active. We do not claim preserved 4K120, VRR, ALLM or input latency.
QUESTIONS FOR LG
- Is a documented, supported API available for third-party consumer TV apps on this model/firmware to access HDMI pixels with user consent, even just a downscaled subtitle region at a modest sampling rate?
- If access requires approved partnership, is there a legitimate entitlement route for this accessibility use case? Which SDK/API, permissions, models and distribution requirements apply?
- Is the external video intentionally rendered through a non-readable hardware plane? Are ext://hdmi and the texture attribute supported for consumer apps?
- Is there a supported way to compose persistent subtitles over native HDMI while preserving Game Optimizer, 4K120 HDR, VRR and ALLM?
- Is getDisplayMedia intentionally unsupported in packaged consumer TV web apps despite being exposed by the web engine?
We request an approved integration route or confirmation of the limitation. We are not seeking a workaround for denied permissions. We can provide the minimal test app and narrowly scoped diagnostic records on request. Thank you.