web/ffmpeg: define multithreading support outside of web worker context

there's no navigator.maxTouchPoints in web worker context, so previously there was no way to detect whether safari is running on ipad or not

web/src/lib/device.ts

@@ -86,7 +86,7 @@ if (browser) {
 
         // enable local processing by default everywhere but android chrome
         defaultLocalProcessing: !(device.is.android && device.browser.chrome),
-        multithreading: !iOS || (iOS && iosVersion >= 18),
+        multithreading: !iOS || iosVersion >= 18,
     };
 
     device.userAgent = navigator.userAgent;

web/src/lib/libav.ts

@@ -5,12 +5,6 @@ import EncodeLibAV from "@imput/libav.js-encode-cli";
 import type { FfprobeData } from "fluent-ffmpeg";
 import type { FFmpegProgressCallback, FFmpegProgressEvent, FFmpegProgressStatus, RenderParams } from "$lib/types/libav";
 
-const ua = navigator.userAgent.toLowerCase();
-const iPhone = ua.includes("iphone os");
-const iPad = !iPhone && ua.includes("mac os") && navigator.maxTouchPoints > 0;
-const iOS = iPhone || iPad;
-const modernIOS = iOS && Number(ua.match(/version\/(\d+)/)?.[1]) >= 18;
-
 export default class LibAVWrapper {
     libav: Promise<LibAVInstance> | null;
     concurrency: number;
@@ -38,7 +32,6 @@ export default class LibAVWrapper {
             this.libav = constructor({
                 ...options,
                 variant: undefined,
-                yesthreads: !iOS || modernIOS,
                 base: '/_libav'
             });
         }

web/src/lib/task-manager/run-worker.ts

@@ -1,4 +1,5 @@
 import { get } from "svelte/store";
+import { device } from "$lib/device";
 import { queue, itemError } from "$lib/state/task-manager/queue";
 
 import { runFFmpegWorker } from "$lib/task-manager/runners/ffmpeg";
@@ -42,6 +43,7 @@ export const startWorker = async ({ worker, workerId, dependsOn, parentId, worke
                     workerArgs.ffargs,
                     workerArgs.output,
                     worker,
+                    device.supports.multithreading,
                     /*resetStartCounter=*/true,
                 );
             } else {

web/src/lib/task-manager/runners/ffmpeg.ts

@@ -16,7 +16,8 @@ export const runFFmpegWorker = async (
     args: string[],
     output: FileInfo,
     variant: 'remux' | 'encode',
-    resetStartCounter = false
+    yesthreads: boolean,
+    resetStartCounter = false,
 ) => {
     const worker = new FFmpegWorker();
 
@@ -34,7 +35,11 @@ export const runFFmpegWorker = async (
             startAttempts++;
             if (startAttempts <= 10) {
                 killWorker(worker, unsubscribe, startCheck);
-                return await runFFmpegWorker(workerId, parentId, files, args, output, variant);
+                return await runFFmpegWorker(
+                    workerId, parentId,
+                    files, args, output,
+                    variant, yesthreads
+                );
             } else {
                 killWorker(worker, unsubscribe, startCheck);
                 return itemError(parentId, workerId, "queue.worker_didnt_start");
@@ -54,6 +59,7 @@ export const runFFmpegWorker = async (
             files,
             args,
             output,
+            yesthreads,
         }
     });
 

web/src/lib/task-manager/workers/ffmpeg.ts

@@ -1,7 +1,13 @@
 import LibAVWrapper from "$lib/libav";
 import type { FileInfo } from "$lib/types/libav";
 
-const ffmpeg = async (variant: string, files: File[], args: string[], output: FileInfo) => {
+const ffmpeg = async (
+    variant: string,
+    files: File[],
+    args: string[],
+    output: FileInfo,
+    yesthreads: boolean = false,
+) => {
     if (!(files && output && args)) {
         self.postMessage({
             cobaltFFmpegWorker: {
@@ -25,7 +31,7 @@ const ffmpeg = async (variant: string, files: File[], args: string[], output: Fi
         })
     });
 
-    ff.init({ variant });
+    ff.init({ variant, yesthreads });
 
     const error = (code: string) => {
         self.postMessage({
@@ -122,6 +128,6 @@ const ffmpeg = async (variant: string, files: File[], args: string[], output: Fi
 self.onmessage = async (event: MessageEvent) => {
     const ed = event.data.cobaltFFmpegWorker;
     if (ed?.variant && ed?.files && ed?.args && ed?.output) {
-        await ffmpeg(ed.variant, ed.files, ed.args, ed.output);
+        await ffmpeg(ed.variant, ed.files, ed.args, ed.output, ed.yesthreads);
     }
 }