Playback

Play, loop and scrub your scene from the viewport's transport bar, and let the frame cache keep it smooth while you work.

Playback controls live along the bottom of the viewport, not on the Timeline, so they stay in reach no matter which panel you have open.

Transport#

Five buttons cover the basics: Go to In Point, Previous Frame, Play / Pause, Next Frame and Go to Out Point. Play toggles playback on and off; every other button in the group stops it first. Dragging the frame number field scrubs directly and stops playback too.

FPS and frame range#

The FPS combo sets the scene's frame rate from a fixed list (8, 12, 15, 24, 25, 30, 48, 50 or 60) and defaults to 24. The Start and End fields set where the playable range begins and ends; End actually stores the frame count rather than the last playable frame, so the last frame you can reach is one less than the number shown. A new scene starts at frame 1 with an End of 25, giving 24 playable frames, exactly one second at the default frame rate. The app will not let the range shrink below one second's worth of frames.

When the transport bar runs out of room, the FPS combo and the Start and End fields move into a menu at the end of it rather than disappearing. Play and Stop stay on the bar however narrow the window gets, and the strip stays centred.

Loop and Ping Pong#

Loop is on by default: reaching the out point during playback wraps the playhead straight back to the in point and keeps going. Ping Pong is off by default; turn it on and playback reverses at the out point instead of wrapping, runs back down to the in point, and then behaves exactly the way Loop is set: if Loop is also on it turns around again and keeps bouncing, and if Loop is off it stops the moment it lands back on the in point.

In and out points#

Set In Point and Set Out Point mark the range Play actually uses, independent of the Start and End of the scene itself, handy for looping one shot out of a longer timeline without changing its length. Moving one point past the other pushes the other one along only if there is no room left between them, so the range can never invert or collapse to nothing. Clear In/Out resets both, and Play then uses the full Start-to-End range again.

Audio sync#

Audio layers stay locked to the playhead. Pressing Play starts the mixed audio at that same instant, pausing stops it immediately, and if you scrub while playing the audio re-syncs to match rather than drifting. Any edit that changes the project's undo history forces the audio to remix before the next frame plays.

Audio scrubbing#

Audio Scrubbing, the button after Loop and Ping Pong, plays the sound under the playhead while playback is stopped: drag the playhead or step a frame and you hear that frame, so a syllable or a beat can be found by ear. It is on by default, works in Animate mode, and is remembered between sessions. What you hear follows the M (Mute) and S (Solo) buttons on each layer's Waveform row, the same as in playback and in the exported file. See Importing video and audio.

What the frame cache does for you#

Once a frame has been composited, Celas Studio keeps a copy so returning to it, during playback or a scrub, can skip re-rendering entirely. The copy is kept on the graphics card, and in memory as well when the frame was drawn by the processor, so a frame you have already played is shown straight from the graphics card with nothing to redraw. Still pictures and painted layers are not redrawn on every frame either. Each of the two stores holds up to the Cache Memory (MB) set in Preferences, 512 MB by default. Once one is full, it drops the frames farthest from the playhead first. The cache is cleared the moment anything that would change the image happens, including a change of view, so it can never show you a stale frame.

While the app is otherwise idle, it quietly renders and caches the ten frames on either side of the playhead ahead of time, so scrubbing near where you are already working tends to feel instant. It waits until you have stopped editing for about a second and a half, and it never takes more than a small share of the processor.

During playback, whenever a frame is quick to show, the spare time goes into preparing the next few frames ahead of the playhead, up to the out point. An occasional heavy frame among light ones is then already waiting when the playhead reaches it, so it is far less likely to stutter on the first pass.

The cache steps aside on its own whenever it cannot guarantee an accurate frame: in Edit mode, while a stroke is in progress, while a symbol or an Action is being edited, while a video frame is still decoding, and while you pan, zoom or drag something on the canvas. Scenes with a video layer, or with a camera that rides a Follow Path or is driven by an Action, are not prepared ahead of time. Onion skin, bone dynamics and scene-wide motion blur no longer turn the cache off: those frames are cached like any other.