Function decodeAudioPeaks

packages/studio-server/src/helpers/waveform.ts:36–75

(audioPath: string)

}

export function decodeAudioPeaks(audioPath: string): Promise<number[]> {
  return new Promise((resolvePromise, reject) => {
    const proc = spawn(
      ffmpegBinary(),
      [
        "-i",
        audioPath,
        "-af",
        "atrim=start_sample=1152",
        "-f",
        "f32le",
        "-ac",
        "1",
        "-ar",
        String(SAMPLE_RATE),
        "-vn",
        "pipe:1",
      ],
      { stdio: ["ignore", "pipe", "ignore"] },
    );

    const chunks: Buffer[] = [];
    proc.stdout?.on("data", (chunk: Buffer) => chunks.push(chunk));
    proc.on("close", (code) => {
      if (code !== 0 && chunks.length === 0) {
        reject(new Error(`ffmpeg exited with code ${code}`));
        return;
      }
      const buf = Buffer.concat(chunks);
      const numSamples = Math.floor(buf.length / 4);
      if (numSamples === 0) {
        reject(new Error("ffmpeg produced no audio samples"));
        return;
      }
      const ab = buf.buffer.slice(buf.byteOffset, buf.byteOffset + numSamples * 4);
      resolvePromise(computePeaks(new Float32Array(ab), PEAK_COUNT));
    });
    proc.on("error", reject);
  });
}

export async function generateWaveformCache(projectDir: string, assetPath: string): Promise<void> {
  const audioPath = join(projectDir, assetPath);