web: draft libav functionality

web/src/lib/libav.ts

@@ -0,0 +1,89 @@
+import mime from "mime";
+import LibAV, { type LibAV as LibAVInstance } from "@imput/libav.js-remux-cli";
+
+type InputFileKind = "video" | "audio";
+
+type FileInfo = {
+    type?: string | null,
+    kind: InputFileKind,
+    extension: string,
+}
+
+type RenderParams = {
+    file: File,
+    output?: FileInfo,
+    args: string[],
+}
+
+export default class LibAVWrapper {
+    libav!: LibAVInstance | null;
+    concurrency: number;
+
+    constructor() {
+        this.concurrency = Math.min(4, navigator.hardwareConcurrency);
+    }
+
+    async init() {
+        if (!this.libav) {
+            this.libav = await LibAV.LibAV({
+                yesthreads: true
+            })
+        }
+    }
+
+    async renderFile({ file, output, args }: RenderParams) {
+        if (!this.libav) throw new Error("LibAV wasn't initialized");
+
+        const inputKind = file.type.split("/")[0];
+        const inputExtension = mime.getExtension(file.type);
+
+        if (inputKind !== "video" && inputKind !== "audio") return;
+        if (!inputExtension) return;
+
+        const input: FileInfo = {
+            kind: inputKind,
+            extension: inputExtension,
+        }
+
+        if (!output) output = input;
+
+        output.type = mime.getType(output.extension);
+        if (!output.type) return;
+
+        const outputName = `output.${output.extension}`;
+
+        const buffer = new Blob([await file.arrayBuffer()]);
+        await this.libav.mkreadaheadfile("input", buffer);
+
+        // https://github.com/Yahweasel/libav.js/blob/7d359f69/docs/IO.md#block-writer-devices
+        await this.libav.mkwriterdev(outputName);
+        let writtenData = new Uint8Array(0);
+
+        this.libav.onwrite = (name, pos, data) => {
+            const newLen = Math.max(writtenData.length, pos + data.length);
+            if (newLen > writtenData.length) {
+                const newData = new Uint8Array(newLen);
+                newData.set(writtenData);
+                writtenData = newData;
+            }
+            writtenData.set(data, pos);
+        };
+
+        await this.libav.ffmpeg([
+            '-threads', this.concurrency.toString(),
+            '-i', 'input',
+            ...args,
+            outputName
+        ]);
+
+        await this.libav.unlinkmkreadaheadfile("input");
+
+        const renderBlob = new Blob(
+            [writtenData],
+            { type: output.type }
+        );
+
+        if (renderBlob.size === 0) return;
+        return renderBlob;
+    }
+}