prevvy

Create a tiled video preview image using ffmpeg... FAST!

Motivation

FFmpeg has this capability built in...

ffmpeg -i ./example.mp4 -y -vframes 1 -q:v 2 -vf 'select=not(mod(n\,23744)),scale=160:-1,tile=6x5:color=Black' output.jpg

... but for long videos, it is very slow. This is because ffmpeg must process every frame in the video, a task that is not well suited for microinstances in datacenters.

This module is designed to accomplish the job of getting a tiled screenshot image FAST, by calling ffmpeg multiple times in parallel, each time using ffmpeg's Input Seeking feature to seek to a point in the video, take a 1 frame snapshot, before combining all the snapshots together (again with ffmpeg) to form a tiled image of snapshots.

Example Output

Caveats

• This project addresses speed for large (several GB) videos only. On small size videos, this module is potentially slower than using FFmpeg's tile filter.
• Frame selection accuracy is not a priority. In other words, the frames selected to be combined into the output are not going to be the same frames that ffmpeg would have chosen, given the same options.

API Usage

  const videoPath = '/tmp/input.mp4'
  const imagePath = '/tmp/output.png';

  let options = {
    input: videoPath,
    output: imagePath,
    width: 128,
    cols: 6,
    rows: 3
  };

  let prevvy = new Prevvy(options);

  /**
   * Optional: the prevvy instance extends EventEmitter, emitting progress events.
   */
  prevvy.on('progress', async (data: { percentage: number }) => {
    await job.updateProgress(data.percentage);
  });

  await prevvy.generate();

CLI Usage

DEBUG=prevvy node ./cli.js generate --input 'https://example.com/my-video.mp4' --output ./my-storyboard.png