OpenCoreMedia

OpenCoreMedia is a pure-Swift implementation target for the Swift-visible Core Media API on platforms where Apple's Core Media framework is unavailable.

The implemented behavior Smokes cover rational CMTime, CMTimeRange, CMTimeMapping, range mapping and folding, CMSampleTimingInfo, immutable video format descriptions, zero-copy image sample buffers backed by OpenCoreVideo, buffer-level attachments with propagation modes, lazily materialized per-sample attachment dictionaries, recursively typed attachment collections, and a segmented zero-copy CMBlockBuffer owner/view path. External and deferred byte leases can be appended or referenced without moving payload bytes. Cross-segment byte operations traverse those leases directly, and contiguous materialization is an explicit allocator-visible copy. Overlapping caller memory is rejected before segmented copy or replacement begins. Every lease is released exactly once after its last buffer or slice owner is destroyed. The current portable surface also includes owned byte attachments, platform-value adapters, multi-sample block buffers, revision-safe asynchronous readiness, injected clocks, anchored timebases, and bounded timed/simple queues. Sample buffers, block buffers, and zero-copy block slices are Sendable on Native, WASM, and Embedded. Foundation Data materialization is isolated in the OpenCoreMediaFoundation product as an explicit copy boundary.

This is not complete Core Media API compatibility. Audio/metadata format families, timer scheduling, queue triggers, real-time lockless platform queues, memory pools, and metadata/tag groups remain outside the completed milestone. See IMPLEMENTATION_PROGRESS.md for current evidence.

Supported production targets

• WebAssembly
• Embedded Swift

Apple-platform builds are used for compatibility and conformance testing. Apps on Apple platforms should import Apple's CoreMedia framework.

Design

Read DESIGN.md before adding public API or buffer implementations. Use APPLE_API_TRACE.md to distinguish implemented, partial, and planned Apple Core Media families.

Build

xcodebuild test \
  -scheme OpenCoreMedia-Package \
  -destination 'platform=macOS' \
  -maximum-test-execution-time-allowance 60 \
  SWIFT_EXEC="$HOME/Library/Developer/Toolchains/swift-6.4.x-DEVELOPMENT-SNAPSHOT-2026-07-17-a.xctoolchain/usr/bin/swiftc"
"$HOME/Library/Developer/Toolchains/swift-6.4.x-DEVELOPMENT-SNAPSHOT-2026-07-17-a.xctoolchain/usr/bin/swift" build \
  --swift-sdks-path "$HOME/Library/org.swift.swiftpm/swift-sdks" \
  --swift-sdk swift-6.4.x-DEVELOPMENT-SNAPSHOT-2026-07-17-a_wasm
"$HOME/Library/Developer/Toolchains/swift-6.4.x-DEVELOPMENT-SNAPSHOT-2026-07-17-a.xctoolchain/usr/bin/swift" build \
  --swift-sdks-path "$HOME/Library/org.swift.swiftpm/swift-sdks" \
  --swift-sdk swift-6.4.x-DEVELOPMENT-SNAPSHOT-2026-07-17-a_wasm-embedded
./scripts/run-wasm-smoke.sh
./scripts/run-embedded-smoke.sh

The Embedded smoke links Swift's Unicode data tables in its final WASI executable because the public attachment contract includes string keys. Library targets compile without an application linker step; an Embedded application using equivalent string operations must link swiftUnicodeDataTables in its WASI executable target.