Importing video and audio

Bringing footage in to rotoscope against and a soundtrack to time to: which formats work on which system, how clips sit on the timeline, how they are decoded, and their sound.

File ▸ Import ▸ Video… adds a Video layer centred on the canvas, and File ▸ Import ▸ Audio… adds an Audio layer. Both appear on the timeline as a coloured clip bar (blue for video, orange for audio) that you can slide and trim like any other editor.

Neither is stored in your project. Celas Studio saves the path to the file, the clip layout and the trims, which keeps the .cls small but means the media has to stay where it is. If it moves, see Missing media.

Formats and platforms#

Most decoding is done by the operating system, so what plays depends on which codecs the machine has.

The extension gets a file past the dialog; the codec inside decides whether it decodes. H.264 in an MP4 is the safest reference footage on both systems. A file the system cannot decode is imported as a layer marked as failed, the same way a failed image import is, rather than as a layer that silently draws nothing.

Video with transparency#

Two kinds of video keep their alpha channel: WebM with transparency (VP9 with alpha) and QuickTime Animation, the .mov format motion graphics are usually exported in. Celas Studio decodes both itself, so they work even where the system decoder would drop the alpha. On Windows, ProRes and HEVC with alpha in a .mov cannot be decoded and come in as failed.

What importing actually does#

Importing a clip reads only its length, size and frame rate, so it opens at once, whatever its length or size, and so does a project with clips in it. Nothing is decoded up front. Frames are decoded when they are needed: during playback a little ahead of the playhead, and after a jump from the frame you jumped to.

Only a few frames around the playhead are kept, so a ten-second clip and a two-hour one take the same memory, and nothing is written to disk. The two transparent formats above are decoded in the background the same way, so they do not slow the canvas down. Exports, still images, shared files and thumbnails always wait for the exact frame of every video in them, also straight after a jump on the timeline.

Clips on the timeline#

A freshly imported file gets one clip starting at frame 1, so the first frame of the animation is the first frame of the media. From there the bar behaves as you would expect:

• Drag the middle of the bar to move the clip in time
• Drag either end to trim the in or out point
• Right-click the bar for Split, which cuts it in two at the frame you clicked, and Remove Clip

One layer can carry several clips from the same file, so you can split a take and re-time the pieces. Frames the clips do not cover are drawn dark on the bar, and play as empty.

Clips are measured in real time. A ten-second clip spans ten seconds of the timeline and plays at its real speed, whatever the frame rate of the file and of the project, and changing the project's frame rate keeps every video and audio clip at its real length. Projects saved before this are converted when they open.

Sound#

Imported video brings its sound with it. The sound belongs to the video layer, so moving or trimming the clip moves its audio with it. Mute is on the layer's right-click menu, and can be undone.

A Video layer and an Audio layer each draw their waveform as a row of its own under the layer, which is what you scrub against when timing an action or a lip-sync. The waveform follows the Level: a fade visibly tapers, a boost grows, and anything boosted past full scale is drawn in red where it will distort. While a layer is silent, because it is muted or another layer is on Solo, its waveform row is drawn dimmed, an Audio layer's bar turns brown, and a Video layer's clip bar loses its waveform band.

The Waveform row has two buttons at the right end of its label: M (Mute) and S (Solo). They decide what is heard in playback, while scrubbing and in the exported file alike. With any layer on Solo, only the soloed layers are heard, and a muted layer stays silent even when it is on Solo. Each click can be undone, and Solo is saved with the project like Mute.

The Properties panel shows an Audio section for both kinds of layer:

Level raises or lowers the layer's volume in decibels. Set +4 dB to boost a quiet take, or key it to animate a fade; it has its own row under the layer on the timeline, with easing like any other channel. -60 dB is treated as silence. Mute and Level are saved with the project.

An Audio layer has no transform: it offers no Position, Rotation, Scale, Anchor or Opacity rows, and it cannot be a parent. A layer dropped onto it in the Layers panel lands beside it instead. The sound card is opened only when something actually plays, so a project with no sound never opens an audio device at all.

Sound plays with the timeline during playback and stops when you stop. With Audio Scrubbing on, dragging the playhead or stepping a frame while playback is stopped plays the sound under that frame: see Playback. On export, audio is mixed into an MP4 and nothing else: MOV, WebM, animated WebP and GIF are silent, and there is no way to export a sound file on its own. See Exporting.

Worth knowing#

• A .webp file always imports as a still image, even if it is animated.
• GIF cannot be imported.
• An .mkv imports but cannot be exported; render to MP4, MOV, WebM or WebP instead.
• A Video layer can be a clipping mask parent, clipping its children to the current video frame. See Masks and clipping.
• An Audio layer is never drawn on the canvas, and has no motion-blur switch in the Timeline.