# Player

A personal native macOS player whose playback code is small enough to own and modify. FFmpeg reads and decodes media; our C++ worker owns playback. SwiftUI owns the controls, Core Audio owns audio output, and Metal presents video.

## Build and run

Requires macOS 15+, Xcode's command-line tools with Swift 6, and Homebrew FFmpeg/pkg-config:

```sh
brew install ffmpeg pkg-config
make
make run
```

The local app is `.build/Player.app`. It links the installed FFmpeg libraries; it is not a standalone distributable bundle. After upgrading FFmpeg, rebuild with `make -B`.

Open a local file with **⌘O**, play/pause with **Space**, and seek with the slider. Files open paused. **⇧⌘W** closes the file; closing the window quits and joins the worker.

## Where to change things

- `Sources/Core/player.h`: the C interface and authoritative state snapshot. Commands enqueue work; poll state for completion. Callers own the opaque handle and must stop using it before destruction.
- `Sources/Core/player.cpp`: single demux/decode worker, bounded buffers, timestamps, audio-master synchronization, paused previews, decoder/resampler drain, seeking, errors, and shutdown. A seek stops output and flushes all old timeline state before resuming.
- `Sources/Core/output.hpp` and `Sources/macOS/Output.mm`: native output contract, allocation-free/nonblocking Core Audio callback and bounded audio ring, latency-aware presentation clock, retained frame mailbox, and Metal YUV conversion. The view can outlive the player safely.
- `Sources/App/PlayerApp.swift`: MainActor state polling, file panel, video host, and controls.
- `Makefile`: compiler/linker commands and app bundle construction. No generated Xcode project or additional build dependency.

## Runnable check

```sh
make check
```

Generates short fixtures and exercises the real playback interface and native outputs: audio/video, video-only, audio-only, pause, paused/playing seek, completion, replay, close, HDR rejection, failed-open recovery, and destruction while playing. It initializes the actual Metal shaders and uses an offscreen native window. It requires a working audio device and graphical macOS session, and plays short sine-wave audio. It is a runtime smoke check, not a mocked clock/device test.

`make check-audio` runs just the audio-quality check. A check-only hook captures actual Core Audio callback PCM into preallocated storage and compares every sample against FFmpeg's reference output for PCM/AAC, 44.1/48 kHz, and coarse container timestamps. A separate gapped fixture verifies that real timestamp gaps remain silent. Release builds contain no capture hook.

Continuous audio uses resampled sample counts for its output timeline; packet timestamp quantization and rounded resampler delay must not insert silence or drop samples between blocks.

Visual correctness, perceived A/V synchronization, and control usability still need a check in the visible app.

## Current limits

Local regular files, automatically selected best audio/video tracks, software decoding, and SDR output. PQ/HLG HDR is rejected rather than rendered incorrectly. No subtitles, selectable tracks, VideoToolbox decoding, rotation/deinterlacing, or network playback yet. Mid-track audio format changes report an error.

Audio buffering is bounded to one second plus one decoded block (up to four seconds); video is bounded to 64 frames/128 MiB. Extremely interleaved files can drop far-future video frames to avoid starving audio; the ceiling and upgrade path are marked at `queueVideo()`. Device/stream latency is accounted for, but device changes during playback are not handled yet.