Leon Serfaty
61 lines
1.8 KiB
TypeScript
61 lines
1.8 KiB
TypeScript
import { promises as fs } from "node:fs";
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import os from "node:os";
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import path from "node:path";
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import { runFfmpeg, ffprobeDuration } from "../ffmpeg";
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/**
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* Concatenate per-segment MP3 buffers into one normalized episode MP3.
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*
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* Segments are re-encoded (not stream-copied) through a single libmp3lame pass
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* with loudness normalization, which guarantees a uniform codec/bitrate and
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* avoids the header/timestamp glitches that `-c copy` concat can produce.
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*/
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export async function stitchMp3(
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segments: Buffer[]
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): Promise<{ data: Buffer; durationSec: number | null }> {
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if (segments.length === 0) throw new Error("No audio segments to stitch");
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const dir = await fs.mkdtemp(path.join(os.tmpdir(), "podcast-distribution-ai-"));
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try {
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const files: string[] = [];
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for (let i = 0; i < segments.length; i++) {
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const file = path.join(dir, `seg_${String(i).padStart(4, "0")}.mp3`);
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await fs.writeFile(file, segments[i]);
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files.push(file);
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}
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// concat demuxer list — forward slashes so it parses on Windows and Linux.
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const listPath = path.join(dir, "list.txt");
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const listBody = files
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.map((f) => `file '${f.split(path.sep).join("/").replace(/'/g, "'\\''")}'`)
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.join("\n");
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await fs.writeFile(listPath, listBody);
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const outPath = path.join(dir, "episode.mp3");
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await runFfmpeg([
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"-y",
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"-f",
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"concat",
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"-safe",
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"0",
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"-i",
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listPath,
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"-af",
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"loudnorm=I=-16:TP=-1.5:LRA=11",
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"-c:a",
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"libmp3lame",
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"-b:a",
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"128k",
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"-ar",
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"44100",
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outPath,
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]);
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const data = await fs.readFile(outPath);
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const durationSec = await ffprobeDuration(outPath);
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return { data, durationSec };
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} finally {
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await fs.rm(dir, { recursive: true, force: true }).catch(() => {});
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}
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}
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