2. From one image to a sequence

In this chapter you will start with one image, then grow it into a 4.5-second sequence. ClipAsm cannot publish three images as one Video. The diagnostic will reveal ClipAsm’s stack model and motivate concat.

Continue your project

Complete Get ClipAsm running first. Stay in the hello-video directory so the starter images remain available.

Create learning.clipasm. This is the file you will develop through the rest of the learning chapters. Leave the generated main.clipasm starter unchanged for comparison.

1. Create a one-image video source

Start with:

clipasm 1

config {
    video {
        width = 320
        height = 180
        fps = 24
    }
    output = "generated/learning.mp4"
}

image("assets/morning.png", 1500ms, contain)

clipasm 1 selects the language version. The video configuration establishes the frame dimensions and frame rate. contain keeps the whole image visible inside that frame. image creates one Video value lasting 1.5 seconds.

2. Validate the one-image source

clipasm validate learning.clipasm

Validation reports 36 frames.

3. Render the one-image Video

clipasm render learning.clipasm

4. Check the one-image Video

Open generated/learning.mp4. Confirm that the morning image appears for 1.5 seconds.

5. Add two more images

Replace the final image call with these three calls:

image("assets/morning.png", 1500ms, contain)
image("assets/meadow.png", 1500ms, contain)
image("assets/evening.png", 1500ms, contain)

6. Validate the three-image source

clipasm validate learning.clipasm

ClipAsm reports E_ENTRYPOINT_OUTPUT_COUNT: three Video values remain, but a source file with output must leave exactly one Video to publish.

7. Explain the diagnostic

When an unfamiliar diagnostic includes a code, ask ClipAsm for its explanation:

clipasm explain E_ENTRYPOINT_OUTPUT_COUNT

8. Examine the stack

Each call leaves its result after the values produced earlier:

image morning  -> [morning]
image meadow   -> [morning, meadow]
image evening  -> [morning, meadow, evening]

This ordered collection is the stack. Each image is valid. The program needs an operation that consumes three Videos and returns one.

9. Add concat

Add concat:

image("assets/morning.png", 1500ms, contain)
image("assets/meadow.png", 1500ms, contain)
image("assets/evening.png", 1500ms, contain)
concat

concat consumes the accessible Videos in stack order and leaves their combined result:

[morning, meadow, evening] -> concat -> [sequence]

10. Validate the sequence

clipasm validate learning.clipasm

Validation now reports 108 frames.

11. Render the sequence

clipasm render learning.clipasm

12. Check the sequence

Reopen generated/learning.mp4. The three 1.5-second scenes play in morning, meadow, evening order.

You now know why statement order matters. A call can consume stack values without receiving them as explicit arguments.

Next, name and reference a clip.