[eugene-mux]

Description

Add a cancellable Media3 adapter for whole-file SDR conversion. Generated files preserve the planned codec family and dimensions and must pass output validation before they can be selected for upload.

Changes

• Use coroutines for dispatch and cancellation, with a cancellable continuation for Media3 callbacks.
• Pin encoder profile, bitrate and keyframe settings, and reject automatic encoder or format fallback.
• Preserve VFR timestamps and choose keyframe intervals from actual frame windows.
• Select the first audio track, copy eligible AAC, and preserve mono/stereo channels and sample rate when encoding other audio.
• Keep capability queries bounded and validate exported codec, profile, audio and timeline.
• Clean SDK-owned partial files on failure or cancellation and suppress late callbacks.

Validation

• 200 library tests pass in each debug/release variant on JDK 17.
• SDK and sample release builds, lint-vital and whitespace checks pass.
• Earlier external, manual emulator checks covered SDR exports, audio selection and cancellation; these historical runs are not reproducible from the repository.
• Physical-device and Mux ingest acceptance remain pending.

---

Note

Medium Risk
New on-device transcode path touches MediaCodec/Media3 export, file lifecycle, and strict codec contracts; failures are gated by validation but bugs could reject valid inputs or leak partial files.

Overview
Adds a cancellable Media3 SDR conversion path for standard-input uploads: SdrConversionAdapter runs preflight, disk allocation, export, and shared output validation on coroutines, delivers a single terminal SdrConversionResult, and deletes or retains partial outputs via SdrGeneratedFile when cleanup fails.

Encoding is intentionally strict. SdrEncodingTargets derives H.264/HEVC bitrate, GOP, and audio plans (including VFR keyframe windows from real presentation timestamps) and rejects HDR, linear transfer, upscaling, and other unproven plans. SdrCapabilityPreflight bounds codec capability queries; Media3SdrExportEngine drives Transformer with no encoder fallback, pinned profiles via StrictSdrEncoderFactory, container-first audio via FirstAudioTrackSelector, and failures on muxer errors or Media3 transformation fallback.

Robolectric tests cover GOP math, adapter lifecycle/cancellation, and Media3 configuration edge cases (device/SOC encoder hints, query budgets).

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[eugene-mux]

@daytime-em thanks for the review, I've added changes you requested.

[daytime-em]

Approved, with one question

[daytime-em]

Is there a particular reason why you chose to enable this? Landscape with a rotation matrix might be better supported by on-device encoders and I don't think standard input is opinionated here.

[eugene-mux]

Good point, thanks. I’ll address this in a later PR in the stack.