Extract the audio stream shape into shared types

The { index, channels, channelLayout } shape was repeated inline in the
preview's main and renderer signatures. Move it to src/common/types.ts as
AudioStreamInfo, and let getFixChannelLayoutFilter take the narrower
AudioChannelInfo it actually needs.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YCf7BBiPqNLUjVoN7rTCF6

src/common/types.ts

@@ -9,6 +9,19 @@ export interface KeyBinding {
 
 export type FfmpegHwAccel = 'none' | 'auto' | 'vdpau' | 'dxva2' | 'd3d11va' | 'vaapi' | 'qsv' | 'videotoolbox';
 
+/**
+ * The parts of an audio stream's ffprobe data needed to decide whether its channel layout
+ * has to be fixed up before ffmpeg can resample or downmix it. See `getFixChannelLayoutFilter`.
+ */
+export interface AudioChannelInfo {
+  channels?: number | undefined,
+  channelLayout?: string | undefined,
+}
+
+export interface AudioStreamInfo extends AudioChannelInfo {
+  index: number,
+}
+
 export type CaptureFormat = 'jpeg' | 'png' | 'webp';
 
 export type TimecodeFormat = 'timecodeWithDecimalFraction' | 'frameCount' | 'seconds' | 'timecodeWithFramesFraction';

src/common/util.ts

@@ -1,4 +1,4 @@
-import type { FfmpegHwAccel } from './types.ts';
+import type { AudioChannelInfo, FfmpegHwAccel } from './types.ts';
 
 export const parseFfprobeDuration = (durationStr: string | undefined) => (
   durationStr != null ? parseFloat(durationStr) : undefined
@@ -41,10 +41,7 @@ export const hasCustomChannelLayout = (channelLayout: string | undefined) => (
 // The `channelmap` filter re-labels the channels without touching the samples, which turns the layout
 // into a plain "N channels" (unspecified) layout. swresample handles those by skipping the rematrixing
 // step entirely, so the stream then behaves exactly as if it had carried no channel layout information.
-export function getFixChannelLayoutFilter({ channels, channelLayout }: {
-  channels?: number | undefined,
-  channelLayout?: string | undefined,
-}) {
+export function getFixChannelLayoutFilter({ channels, channelLayout }: AudioChannelInfo) {
   if (channels == null || channels <= 0 || !hasCustomChannelLayout(channelLayout)) return undefined;
   return `channelmap=${Array.from({ length: channels }, (_, i) => i).join('|')}`;
 }

src/main/ffmpeg.ts

@@ -10,7 +10,7 @@ import type { Readable } from 'node:stream';
 import { app, clipboard, nativeImage } from 'electron';
 
 import { platform, arch, isWindows, isLinux } from './util.js';
-import type { CaptureFormat, FfmpegHwAccel } from '../common/types.js';
+import type { AudioStreamInfo, CaptureFormat, FfmpegHwAccel } from '../common/types.js';
 import type { FFprobeFormat } from '../common/ffprobe.js';
 import isDev from './isDev.js';
 import logger from './logger.js';
@@ -594,7 +594,7 @@ const encode = true;
 export function createMediaSourceProcess({ path, videoStreamIndex, audioStreams, seekTo, size, fps, rotate, forceColorspace, ffmpegHwaccel }: {
   path: string,
   videoStreamIndex?: number | undefined,
-  audioStreams: { index: number, channels?: number | undefined, channelLayout?: string | undefined }[],
+  audioStreams: AudioStreamInfo[],
   seekTo: number,
   size?: number | undefined,
   fps?: number | undefined,
@@ -666,7 +666,7 @@ export function createMediaSourceProcess({ path, videoStreamIndex, audioStreams,
 
     if (audioStreams.length > 0) {
       // some streams have a channel layout that ffmpeg cannot resample or downmix, so relabel it first
-      const getAudioFilters = (stream: typeof audioStreams[number], rest: string[]) => {
+      const getAudioFilters = (stream: AudioStreamInfo, rest: string[]) => {
         const filters = [getFixChannelLayoutFilter(stream), ...rest].filter((filter) => filter != null);
         return filters.length > 0 ? filters.join(',') : 'anull';
       };

src/renderer/src/MediaSourcePlayer.tsx

@@ -8,7 +8,7 @@ import isDev from './isDev';
 import type { ChromiumHTMLVideoElement } from './types';
 import type { FFprobeStream } from '../../common/ffprobe';
 import { getFrameDuration } from './util';
-import type { FfmpegHwAccel } from '../../common/types';
+import type { AudioStreamInfo, FfmpegHwAccel } from '../../common/types';
 
 const { compatPlayer: { createMediaSourceStream } } = window.require('@electron/remote').require('./index.js');
 
@@ -18,7 +18,7 @@ async function startPlayback({ path, slaveVideo, masterVideo, videoStreamIndex,
   slaveVideo: ChromiumHTMLVideoElement,
   masterVideo: ChromiumHTMLVideoElement,
   videoStreamIndex?: number | undefined,
-  audioStreams: { index: number, channels?: number | undefined, channelLayout?: string | undefined }[],
+  audioStreams: AudioStreamInfo[],
   seekTo: number,
   signal: AbortSignal,
   size?: number | undefined,