✨ fix: reassemble JPEG frame boundaries and report ffmpeg progress

src/videoProcessor.ts

@@ -1,40 +1,129 @@
 import ffmpeg from "fluent-ffmpeg";
 import fs from "fs";
 import { FramesContainer } from "./frames";
+import { logger } from "./logger";
+
+const SOI = Buffer.from([0xff, 0xd8]);
+const EOI = Buffer.from([0xff, 0xd9]);
+
+export interface ProcessOptions {
+    maxDimension?: number;
+}
+
+class JpegFrameSplitter {
+    private buffer = Buffer.alloc(0);
+
+    push(chunk: Buffer): Buffer[] {
+        this.buffer = Buffer.concat([this.buffer, chunk]);
+        const frames: Buffer[] = [];
+
+        for (;;) {
+            const start = this.buffer.indexOf(SOI);
+            if (start === -1) break;
+            const end = this.buffer.indexOf(EOI, start + SOI.length);
+            if (end === -1) break;
+
+            const frameEnd = end + EOI.length;
+            frames.push(this.buffer.subarray(start, frameEnd));
+            this.buffer = this.buffer.subarray(frameEnd);
+        }
+
+        return frames;
+    }
+}
+
+export async function process(
+    path: string,
+    output: string,
+    options: ProcessOptions = {}
+): Promise<void> {
+    const maxDimension = options.maxDimension ?? 320;
 
-export async function process(path: string, output: string): Promise<void> {
     return new Promise((resolve, reject) => {
         ffmpeg(path).ffprobe((err, data) => {
             if (err) {
-                reject(new Error("An error occurred: " + err.message));
+                reject(new Error("ffprobe failed: " + err.message));
                 return;
             }
 
-            if (!data.streams[0].r_frame_rate) {
-                reject(new Error("Unable to get video fps"));
+            const stream = data.streams?.[0];
+            const rate = stream?.r_frame_rate;
+            const fps = rate ? parseFloat(rate) : NaN;
+            if (!Number.isFinite(fps) || fps <= 0) {
+                reject(new Error("Unable to determine a valid video fps"));
                 return;
             }
 
-            const videoData: FramesContainer = {
-                frames: [],
-                fps: parseFloat(data.streams[0].r_frame_rate),
+            const nbFrames = stream?.nb_frames
+                ? parseInt(String(stream.nb_frames), 10)
+                : NaN;
+            const duration = Number(data.format?.duration ?? stream?.duration);
+            const totalFrames = Number.isFinite(nbFrames)
+                ? nbFrames
+                : Number.isFinite(duration)
+                  ? Math.round(duration * fps)
+                  : undefined;
+
+            const videoData: FramesContainer = { frames: [], fps };
+            const splitter = new JpegFrameSplitter();
+
+            let settled = false;
+            const fail = (message: string) => {
+                if (settled) return;
+                settled = true;
+                reject(new Error(message));
+            };
+
+            const reportProgress = (count: number) => {
+                if (totalFrames && totalFrames > 0) {
+                    const pct = Math.min(
+                        100,
+                        Math.round((count / totalFrames) * 100)
+                    );
+                    globalThis.process.stdout.write(
+                        `\rGenerating frames: ${count}/${totalFrames} (${pct}%)`
+                    );
+                } else {
+                    globalThis.process.stdout.write(
+                        `\rGenerating frames: ${count}`
+                    );
+                }
             };
 
             const ffvideo = ffmpeg(path)
-                .outputOptions("-f image2pipe")
-                .outputOptions("-vf format=gray")
-                .on("error", (err) => {
-                    console.log("An error occurred: " + err.message);
-                });
+                .outputOptions("-c:v", "mjpeg")
+                .outputOptions("-q:v", "3")
+                .outputOptions(
+                    "-vf",
+                    `format=gray,scale=w=${maxDimension}:h=${maxDimension}:` +
+                        `force_original_aspect_ratio=decrease`
+                )
+                .outputOptions("-f", "image2pipe")
+                .on("error", (err) => fail("ffmpeg failed: " + err.message));
 
             const ffstream = ffvideo.pipe();
+            ffstream.on("error", (err: Error) =>
+                fail("ffmpeg stream error: " + err.message)
+            );
             ffstream.on("data", (chunk: Buffer) => {
-                videoData.frames.push(chunk);
+                for (const frame of splitter.push(chunk)) {
+                    videoData.frames.push(frame);
+                }
+                reportProgress(videoData.frames.length);
             });
 
             ffstream.on("end", () => {
+                if (settled) return;
+                if (videoData.frames.length === 0) {
+                    fail("No frames were decoded from the video");
+                    return;
+                }
+                settled = true;
+                globalThis.process.stdout.write("\n");
                 fs.writeFileSync(output, JSON.stringify(videoData));
-                console.log("Frames saved to", output);
+                logger.info(
+                    `Saved ${videoData.frames.length} frames to ${output}`
+                );
                 resolve();
             });
         });