Golf Swing Phase Detection

What Swing Phase Detection Does

On a golf swing recording that has motion capture data, Swing Catalyst analyzes the tracked body pose and places bookmarks at the ten key positions of the swing. You no longer have to drag three markers into place by eye.

Detected bookmarks behave exactly like bookmarks you set yourself. They drive playback navigation, the phase colors on the skeleton, the timing key metrics, and synchronized comparison between two swings. You can still move any of them afterwards.

The ten positions

These are often written P1 to P10.

Detected phases appear as markers on the playback timeline, one per position, in swing order:

Move between them the way you move between any markers. The frame and time readout beside the timeline tells you where you are.

What a recording needs

• A golf swing recording. Other sports and activities are unaffected and keep their existing bookmarks.
• Motion capture data. Recordings made without motion capture can be reprocessed to add it. See Adding motion capture to existing recordings .
• A camera tagged as a face-on angle. Detection only uses motion capture from a camera whose angle is set to Face on left or Face on right. A face-on clip that was never tagged reads as “not face-on”.

Club tracking is helpful but not required. Without a usable club track, Swing Catalyst falls back to estimating the classic three positions (Start of Take Away, Top of Swing, Impact) from body pose alone. Those three markers are labeled with the suffix (estimated from body pose) so you can tell them apart from a full detection.

When Bookmarks Get Updated

Recordings made before phase detection existed, or with an older version of the detector, can have their bookmarks brought up to the current detection. Opening one applies the detected positions either way. What changes is whether you are then asked about it. That comes down to one question: have you moved any of that recording’s markers yourself?

The first time detection is applied to a recording, the markers it had at that moment are saved with the recording as its earlier markers. That set includes any you had moved yourself. It stays with the recording after you close it and after you restart the software. See Going back to earlier markers for what it does and does not cover.

Your markers are not left alone while you decide. The detected positions are applied first so that you judge them on screen rather than from a description.

The notification

When a recording picks up the detected phases on its own, a notification reading Swing phases updated appears with a Revert button and a Dismiss button. Revert puts the previous bookmarks back.

The very first time this happens, the notification explains itself in full instead. You see this once, not once per recording:

Swing phases are now detected automatically on this recording. Use Revert to go back, or control this under Settings > General > Swing phase detection.

Recordings made with the current version get their detected positions as they open, which is not a change to anything, so no notification appears for them.

The offer banner

When you open a recording whose markers you moved yourself, the detected positions are applied so you can see them, and a banner appears at the bottom of the video area asking what to do about them:

The detected swing phases have been applied over the markers you positioned yourself. Save them, or put your own markers back.

The markers the recording had are saved first, so you can put them back while you look or later.

• Save new phases keeps the detected positions. Your earlier markers stay available under Restore my earlier markers in the marker menu.
• Use old phases puts your markers back exactly where they were and stops offering for this recording. Detect phases still works if you change your mind later.
• Always replace my markers with detected phases is a checkbox next to Save new phases. Tick it before saving, and the same click sets your preference so you are not asked again on other recordings where you have moved markers. Ticking it and then choosing Use old phases changes nothing.

The close button in the corner of the banner hides it without answering it, and so do the Esc key and closing the recording. The detected positions stay in all three cases, and the banner does not come back for that recording. Use Restore my earlier markers in the marker menu if you want your own markers back later.

With two recordings open side by side, both show the detected positions and one banner asks about them.

Choosing whether to be asked

Open Settings → General → Swing phase detection. There is one setting, When you have moved markers yourself:, with two options.

This setting covers that one case and nothing else. A recording whose markers you never moved always gets the detected phases, whichever option you pick. To keep one particular recording as it is, use Use old phases on its banner, or one of the marker menu items described in Going back to earlier markers .

Running Detection Yourself

The detect button sits at the right-hand end of the playback bar, past the frame and time readout. It is outlined here:

Its tooltip tells you what pressing it will do, and changes with the state of the recording:

Unlock the bookmark bar and you get a second way in: each open recording has a row with a button labeled Detect phases, or Redo detection on a recording that has been detected before.

Detection runs whenever you ask for it. No recording can end up in a state where the button refuses: not one you chose Use old phases on, not one whose earlier markers you restored, not even one where you moved every marker by hand.

If the recording has markers you positioned yourself, you are asked to confirm first, in a dialog titled Detect swing phases:

This recording has markers you positioned yourself. Detecting swing phases replaces them with the detected positions. You can undo this from the marker menu. Continue?

When two recordings are open side by side, the button opens a small menu so you can choose Detect phases A or Detect phases B.

If the recording has no motion capture data yet, the button offers to add it first and asks:

This recording has no motion capture data yet. Reprocessing it first will run pose tracking, then swing phases will be detected from the result. Continue?

The reprocess can take several minutes on a long clip.

When the button is grayed out, hover it. The tooltip always explains why (see If detection is not available ).

Markers You Set Yourself

A bookmark you dragged or placed yourself gets replaced by detection. Opening the recording applies the detected positions over it and the banner asks what to do; running Detect phases asks you to confirm and then replaces it.

What is saved depends on whether the recording has been detected before:

• First detection on a recording. The markers it has at that moment, including every one you moved yourself, are saved as its earlier markers. Restore my earlier markers puts them back.
• Detection again on a recording that already carries detected phases. The earlier markers from the first detection are kept as they were. Any marker you moved since that first detection is replaced, and it is not added to the saved set. There is no way to get that later position back other than dragging the marker there again.

A recording where you positioned every single marker can still be detected: click Detect phases, confirm, and the detected positions are written over them.

After detection you can still drag any marker. A recording that already carries detected phases is never detected again on its own. A marker you move stays where you put it until you run detection yourself.

Unlock the bookmark bar to see where the current bookmarks came from. A short label reads Phases detected, Edited by you, or Set manually, and the line beside it changes to match. On a detected recording it reads:

Ten swing phases from motion capture. Drag any marker to correct it.

Going Back to Earlier Markers

If the detected positions are wrong for a particular swing, put the old ones back.

1. Unlock the bookmark bar with the bookmarks button on the playback bar (or Ctrl + B).
2. Open that recording’s marker menu with the three-dot button at the end of its row, tooltip More marker actions.
3. Choose Restore my earlier markers.

The item only appears while there is something to restore. You can also use the Revert button on the notification, while it is still showing.

Restoring always asks first, in a dialog titled Restore earlier markers:

Your markers go back to where they were before phase detection ran, including any you had moved yourself at the time. Anything you have adjusted since then is replaced. This recording also stops detecting phases automatically, but you can run Detect phases yourself at any time. Restore your earlier markers?

So restoring does two things. It puts back the markers the recording had before detection first ran, including any you had moved by hand at that time, and it stops that one recording from picking up detected phases on its own. Markers you moved after that first detection are not part of the saved set and are replaced. The stop is not permanent: clicking Detect phases on it later detects again, and the recording goes back to normal.

Going back to the old three markers

The same menu offers Use old 3-point markers on a golf swing. It discards the current markers and puts back the three the recording used before ten-phase detection existed. Because that throws away the detected phases, it asks first, in a dialog titled Use old 3-point markers:

Your markers go back to the three this activity starts with. Any detected swing phases and any positions you set yourself are replaced. This recording also stops detecting phases automatically, but you can run Detect phases yourself at any time. Use the old 3-point markers?

Like restoring, this stops that golf recording from picking up detected phases on its own, and clicking Detect phases starts it again.

Every other activity shows Use the default markers for this activity instead, because those presets are not three markers. Swing phase detection is golf only, so on those activities there is nothing to switch off and the confirmation is shorter, titled Use the default markers:

Your markers go back to this activity’s defaults. Any positions you set yourself are replaced. Use the default markers?

Cropping Playback to the Marked Range

Long clips usually contain a lot of setup and walking about. The crop button on the playback bar, next to the loop button, trims playback to the part that matters. It is a simple on and off: click it to crop, click it again for the whole recording.

When cropping is on, the software chooses how tight the window is. You do not pick this.

The button’s icon changes with the window as well, so you can tell at a glance without hovering.

The button works on any recording, in any sport, that has at least two bookmarks spaced far enough apart to crop between. Detected golf phases are one source of those bookmarks, not a requirement. Your choice is remembered for the next recording and after restarting the software. Nothing is trimmed from the recording itself: this only changes what you play back and scrub through.

Doing Several Recordings at Once

To bring a whole session up to date, select the recordings in the Explorer, right-click and choose Reprocess motion capture & detect swing phases. The batch runs in the background while you keep working, and can be canceled.

The batch updates the bookmarks as it goes, on every selected golf swing whose markers you never moved. Recordings whose markers you did move are the exception: they keep their markers and are counted separately in the summary, and the offer banner puts the choice in front of you the next time you open one. If your setting is Replace my markers with the detected phases, those recordings are updated along with the rest.

You get a summary banner when the batch finishes, so it never ends in silence. It reports what happened to each recording, and offers Revert all when there is something to revert. Expand Show details and one of the rows counts the recordings it left alone, for example “3 kept the markers you positioned yourself; open them to use the detected phases”.

The full flow, including what happens when recordings fail, is in Adding motion capture to existing recordings .

Timing Metrics From the Detected Phases

Once the phases are in place, three golf timing metrics become available in the Key Metrics databox: Tempo Ratio, Transition Duration and Release Timing. They are calculated purely from where the bookmarks sit, so they are only as good as the bookmark positions. See Key Metrics .

If Detection Is Not Available

The detect button is only shown on golf swing recordings. When it is there but grayed out, hover it, or read the message on the bookmark bar.

Why the button is unavailable

After a reprocess that you started from this button, the phases are not shown until you close the recording and open it again (see the warning under Running detection yourself ).

Having moved the markers yourself does not disable the button, and neither does having detected the recording before. In those cases the button stays available and asks you to confirm, or re-runs detection.

Why detection found nothing

Each message has two lines. The first names the problem and the second says what to do. The table quotes both in full.

“Take” in these messages means a recording.

Detection used the wrong handedness

If a player’s handedness is not set in their profile, detection assumes right-handed and the button tooltip says so. Set handedness on the student profile and run detection again.

Keyboard Shortcuts

Golf swing recordings now have ten bookmarks, and the number keys reach all of them. 1 to 9 and 0 jump to bookmarks 1 to 10, Page Up and Page Down step between them, and Ctrl + Shift + I and Ctrl + Shift + T synchronize two recordings on Impact and Top of Swing. The full list is in Keyboard shortcuts and Hotkeys .

See also: What are bookmarks? · Motion Capture Guide · Object Detection · Key Metrics