Technique Lab

How to analyse a technique video frame by frame

1. Load a clip from your phone or computer. It stays on your device, so nothing is uploaded and nothing is shared.
2. Drop the playback speed to 0.25x or 0.1x, then use the frame buttons to walk through the key moment one frame at a time. Hold a frame button to run through a sequence.
3. Pick a drawing tool and mark the picture: a straight line for shoulder tilt, a box around the hands, an arrow for direction of travel, or the angle tool for a joint measurement.
4. For the angle tool, tap three points in order: the first limb, then the joint itself, then the second limb. Drag any of the three handles and the degrees update live.
5. Switch to compare mode to load a second clip, set a sync point on each video at the same moment of the movement, then lock the transport so both clips step together.
6. Save the marked-up frame as a PNG, or record a slow motion clip with your drawings burned in so you can send it to the athlete.

Why use ZillaKit's Technique Lab?

Coaching apps for video analysis usually want an account, a subscription and a copy of your footage on their servers. Technique Lab does the same core job with none of that. The video is opened straight from your device with a local object URL, every frame is decoded by the browser you already have, and the drawing layer is a plain canvas sitting on top. No file is ever transmitted, which matters a great deal when the footage is of a junior athlete, a client session or a competition your club would rather keep private.

The parts that coaches actually use are all here and all free. Playback runs down to a tenth of real speed, frame stepping walks through a swing or a lift one frame at a time, and a fine scrub bar with a live time and frame readout makes it easy to land on the exact moment of contact, release or lockout. The drawing layer covers freehand pen, straight lines, arrows, circles and boxes, plus a three point angle tool that reports the joint angle in degrees and keeps updating while you drag the handles. Every set of drawings is stored against the frame time it was made at, so you can build up several marked positions in one clip and jump back to any of them from the marker list.

Side by side comparison is the part that usually sits behind a paywall elsewhere. Load a second clip, set a sync point on each one at the same moment of the movement, and the locked transport drives both videos together while keeping the offset, so a before and after or a model versus athlete comparison lines up properly. Each side can be mirrored independently, which makes a left handed player directly comparable with a right handed one. When you are done, export a still frame with the drawings baked in, or record a slow motion clip as a WebM file to share. There is no watermark, no signup and no upload queue.

FAQ

Are my videos uploaded anywhere?

No. The clip is opened locally with a browser object URL and every frame is decoded and drawn on your own device. Nothing is sent to a server, so private training footage stays private.

How accurate is the frame stepping?

Browsers seek video by time, not by frame number, so accuracy depends on the file. Where your browser supports the video frame callback API, the tool reads the real presentation time of each frame, works out the true frame interval during playback and steps by exactly that amount. Where it is not available, stepping uses the frame rate you pick in the menu and the frame number shown is an estimate. Heavily compressed files with long gaps between keyframes can also seek less precisely than files recorded at a high bit rate.

Which video files can I open?

Anything your browser can play natively. MP4 with H.264 video and WebM work almost everywhere. MOV files from phones usually work, and HEVC or ProRes files depend on the browser and device. If a clip refuses to load, convert it to MP4 first and try again.

How do I measure a joint angle?

Choose the angle tool and tap three points in order: a point along the first segment, then the joint itself as the vertex, then a point along the second segment. The tool draws both rays and an arc and prints the angle in degrees. Drag any of the three round handles to fine tune it, and add as many angles as you need on the same frame.

Can I compare two videos and keep them in sync?

Yes. Switch to compare mode, load a second clip, then set a sync point on each video at the same moment of the movement, such as ball contact or the bar leaving the floor. With sync locked, the main transport plays, scrubs and frame steps both clips together while holding that offset, and each side can be mirrored on its own.

Can I save a slow motion clip with the drawings on it?

Yes, where the browser supports canvas capture and media recording. Set an in point and an out point, then record. The tool composites the video and your drawings into a WebM file at the playback speed you chose. The recording has no audio, and the button is hidden automatically on browsers that cannot do it.

Does it use AI or pose detection?

No. There is no model, no tracking and no automatic skeleton. Every line and angle is placed by you, which keeps the tool fast, predictable and completely offline once the page has loaded.

Does it work on a phone at training?

Yes. The layout stacks to a single column, the controls are sized for fingers, pinch zooms the picture and holding a frame button steps repeatedly. Recording a long clip is heavier work on a phone, so keep exported clips short.