https://github.com/sauravpanda/stepback
iOS practice tool for learning dance from your own video library. Slow-mo without pitch-shift, loop hard sections, frame-step, and beat-locked step timing. SwiftUI + SwiftData, iOS 17+, zero dependencies.
https://github.com/sauravpanda/stepback
avfoundation beat-detection dance ios practice-tool swiftdata swiftui video-playback west-coast-swing
Last synced: 16 days ago
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iOS practice tool for learning dance from your own video library. Slow-mo without pitch-shift, loop hard sections, frame-step, and beat-locked step timing. SwiftUI + SwiftData, iOS 17+, zero dependencies.
- Host: GitHub
- URL: https://github.com/sauravpanda/stepback
- Owner: sauravpanda
- License: mit
- Created: 2026-04-21T18:27:26.000Z (about 2 months ago)
- Default Branch: main
- Last Pushed: 2026-05-15T00:16:36.000Z (25 days ago)
- Last Synced: 2026-05-15T02:32:25.482Z (25 days ago)
- Topics: avfoundation, beat-detection, dance, ios, practice-tool, swiftdata, swiftui, video-playback, west-coast-swing
- Language: Swift
- Homepage:
- Size: 153 KB
- Stars: 1
- Watchers: 0
- Forks: 0
- Open Issues: 13
-
Metadata Files:
- Readme: README.md
- Contributing: CONTRIBUTING.md
- License: LICENSE
Awesome Lists containing this project
README
# StepBack
A practice tool for learning dance from your own video library. iOS only, SwiftUI.
Slow footage down without pitch-shifting the audio, loop hard sections, frame-step through tricky moves, tag clips by event, compare yourself against the instructor side-by-side, and — critically — check whether your stepping actually lands on the beat.
> Primary user: the author. Daily-use quality, not App-Store-polish. No accounts, no backend, no cloud sync in v1.
## Why this exists
Apple's stock Photos/Videos tools can't do tight A/B loops, pitch-preserved slow-mo, or beat-locked step timing. Existing dance apps either don't combine these or lock them behind subscriptions and sync. StepBack does the one specific thing it needs to do, on-device, with nothing but Apple's SDKs.
## Features
**v1 — core practice loop**
- Import videos from Photos (multi-select, no copies — references `PHAsset` identifiers)
- Auto-group clips into events by creation date (24h gap = new event)
- Variable-speed playback (0.25×–1.5×) with pitch preservation
- A/B loop with draggable region, saved as named markers with preferred speed
- True frame-by-frame stepping (`AVPlayerItem.step(byCount:)`)
- Mirror mode
- Side-by-side compare view with synced playback
**v1.5 — beat detection**
- On-device BPM detection via STFT + autocorrelation (Accelerate / vDSP)
- Beat ticks on the scrubber, live count-in-measure indicator
- User-driven downbeat anchoring ("tap on beat 1"), persisted per clip
- Step-timing mode: tap every step, see ms-precise offset from nearest beat as a colored histogram
**v2 — later**
Pose tracking overlay (Vision), speed ramps, ghost overlay recording, iCloud sync. See the [roadmap](https://github.com/sauravpanda/stepback/issues).
## Tech
- SwiftUI + SwiftData (iOS 17+)
- AVKit / AVFoundation for playback and frame stepping
- PhotoKit for library access (no video copies)
- Vision for pose tracking (v2)
- Accelerate (vDSP) for FFT-based beat detection
- **Zero third-party dependencies.**
## Project structure
```
StepBack/
StepBackApp.swift @main, SwiftData container
Models/Models.swift DanceClip, Tag, LoopMarker
Views/
LibraryView.swift Grid of clips, tag filter, import
PracticeView.swift The core player screen
CompareView.swift Side-by-side synced playback
Services/
PhotosService.swift PHAsset -> AVURLAsset, thumbnails
AutoTagService.swift Cluster clips by time -> events
PracticePlayerViewModel.swift Playback state, loop, speed, step timing
BeatDetector.swift Onset envelope + tempo autocorrelation
AIServices.swift Pose tracking stubs (v2)
Utilities/Theme.swift Colors, design tokens
```
## Building
1. Open `StepBack.xcodeproj` in Xcode 15+
2. Signing & Capabilities → pick your Apple ID team
3. Cmd+R with your iPhone plugged in
Free Apple ID signing: sideloaded apps expire in 7 days; re-run from Xcode to refresh.
See [BUILD.md](docs/BUILD.md) for details.
## Design tokens
Dark UI, hot-pink accent. No generic AI-gray look.
- `bg #0A0A0F` · `surface #171720` · `surfaceElevated #22222C`
- `accent #FF3B7F` · `accentSoft` = accent @ 15% alpha
- Speed pill colors: cyan <0.5×, green <1×, white =1×, orange >1×
- SF Rounded for display, SF Pro for body, SF Mono for timestamps
## Status
Pre-v1. Tracking progress via [issues](https://github.com/sauravpanda/stepback/issues) and [milestones](https://github.com/sauravpanda/stepback/milestones).
## License
MIT — see [LICENSE](LICENSE).