Technical feasibility: native P7 FEL playback via in-app dual-layer composition?

Video Playback
1

Hi James and team,

Currently, Infuse handles Profile 7 FEL content by falling back to HDR10 or requiring users to re-encode to Profile 8 (which drops the enhancement layer and loses the full 12-bit precision). I’d like to discuss whether a native in-app decoding path is technically feasible on iOS/tvOS.

The core idea:
Instead of relying on VideoToolbox’s P7 support (which Apple does not expose), decode the Base Layer (BL) and Enhancement Layer (EL) as two independent HEVC streams within the app, then compose them in the IQ domain before output.

Proposed pipeline:

  1. Container parsing

    • Dual-track MKV/MP4: EL as a separate video stream
    • Single-track in-band: demux DOVIEL NAL units from the HEVC bitstream
    • BDMV ISO: parse MPLS → CLIP → SSIF sub-path for dual-layer video

  2. Decoding

    • BL: HEVC Main10, Level 5.1/6.1, YUV420 10-bit → VideoToolbox hardware decode
    • EL: independent HEVC stream (typically 1080p or 4K) → VideoToolbox hardware decode, parallel to BL
    • Frame sync via RASL/CRA management to align PTS after seek

  3. Composition

    • EL treated as residual layer, combined with BL in IQ domain
    • NLQ inverse quantization to reconstruct 12-bit signal
    • MMR chroma mapping via RPU coefficients for full YCbCr 12-bit recovery

  4. RPU metadata

    • Parse Dolby Vision RPU NAL for L1 (per-shot tone mapping), L2 (global), L5 (active picture area), L6 (display mapping)

  5. Output

    • Composed 12-bit DV signal → CVPixelBuffer → AVSampleBufferDisplayLayer (local) or HDMI passthrough to DV-certified display

Key questions for the team:

  • Is the Dolby Vision licensing agreement for Infuse flexible enough to allow in-app composition rather than relying solely on system-level DV pipelines?
  • For 4K FEL, dual parallel HEVC decodes plus real-time composition would be heavy. Has Firecore evaluated whether A15/A17/M-series chips can sustain this thermally?
  • Would this path be gated to Apple TV only, or is iPhone/iPad performance viable for shorter sessions?

I understand this is a significant engineering effort. My goal is simply to understand whether this is on the technical radar or blocked by factors outside Firecore’s control (licensing, Apple API limitations, etc.).

Thanks for any insight you can share.

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Native Profile 7 FEL playback
2

2 posts were merged into an existing topic: Native Profile 7 FEL playback (full enhancement layer, no conversion)