add native export ffmpeg helpers

electron/ipc/nativeVideoExport.ts

@@ -0,0 +1,172 @@
+const NATIVE_EXPORT_INPUT_BYTES_PER_PIXEL = 4
+
+export type NativeExportEncodingMode = 'fast' | 'balanced' | 'quality'
+
+export type NativeVideoExportAudioMode = 'none' | 'copy-source' | 'trim-source' | 'edited-track'
+
+export interface NativeVideoExportStartOptions {
+	width: number
+	height: number
+	frameRate: number
+	bitrate: number
+	encodingMode: NativeExportEncodingMode
+}
+
+export interface NativeVideoExportAudioSegment {
+	startMs: number
+	endMs: number
+}
+
+export interface NativeVideoExportFinishOptions {
+	audioMode?: NativeVideoExportAudioMode
+	audioSourcePath?: string | null
+	trimSegments?: NativeVideoExportAudioSegment[]
+	editedAudioData?: ArrayBuffer
+	editedAudioMimeType?: string | null
+}
+
+export function getNativeVideoInputByteSize(width: number, height: number): number {
+	return width * height * NATIVE_EXPORT_INPUT_BYTES_PER_PIXEL
+}
+
+export function parseAvailableFfmpegEncoders(stdout: string): Set<string> {
+	const encoders = new Set<string>()
+
+	for (const line of stdout.split(/\r?\n/)) {
+		const match = line.match(/^\s*[A-Z.]{6}\s+([a-z0-9_]+)/i)
+		if (match?.[1]) {
+			encoders.add(match[1])
+		}
+	}
+
+	return encoders
+}
+
+export function getPreferredNativeVideoEncoders(platform: NodeJS.Platform): string[] {
+	switch (platform) {
+		case 'darwin':
+			return ['h264_videotoolbox', 'libx264']
+		case 'win32':
+			return ['h264_nvenc', 'h264_qsv', 'h264_amf', 'h264_mf', 'libx264']
+		case 'linux':
+			return ['h264_nvenc', 'h264_qsv', 'libx264']
+		default:
+			return ['libx264']
+	}
+}
+
+function getLibx264ModeArgs(encodingMode: NativeExportEncodingMode): string[] {
+	switch (encodingMode) {
+		case 'fast':
+			return ['-preset', 'ultrafast', '-tune', 'zerolatency']
+		case 'quality':
+			return ['-preset', 'slow']
+		case 'balanced':
+		default:
+			return ['-preset', 'medium']
+	}
+}
+
+function getBitrateArgs(bitrate: number): string[] {
+	const effectiveBitrate = Math.max(1_500_000, Math.round(bitrate))
+	const maxRate = Math.max(effectiveBitrate, Math.round(effectiveBitrate * 1.2))
+	const bufferSize = Math.max(maxRate * 2, effectiveBitrate * 2)
+
+	return [
+		'-b:v',
+		String(effectiveBitrate),
+		'-maxrate',
+		String(maxRate),
+		'-bufsize',
+		String(bufferSize),
+	]
+}
+
+export function buildNativeVideoExportArgs(
+	encoder: string,
+	options: NativeVideoExportStartOptions,
+	outputPath: string,
+): string[] {
+	const args = [
+		'-y',
+		'-hide_banner',
+		'-loglevel',
+		'error',
+		'-f',
+		'rawvideo',
+		'-pix_fmt',
+		'rgba',
+		'-s:v',
+		`${options.width}x${options.height}`,
+		'-framerate',
+		String(options.frameRate),
+		'-i',
+		'pipe:0',
+		'-vf',
+		'vflip',
+		'-an',
+		'-c:v',
+		encoder,
+		'-g',
+		String(Math.max(1, Math.round(options.frameRate * 5))),
+		...getBitrateArgs(options.bitrate),
+	]
+
+	if (encoder === 'libx264') {
+		args.push(...getLibx264ModeArgs(options.encodingMode))
+	}
+
+	args.push('-pix_fmt', 'yuv420p', '-movflags', '+faststart', outputPath)
+	return args
+}
+
+function formatFfmpegSeconds(milliseconds: number): string {
+	return (milliseconds / 1000).toFixed(3)
+}
+
+export function buildTrimmedSourceAudioFilter(
+	segments: NativeVideoExportAudioSegment[],
+): string | null {
+	if (segments.length === 0) {
+		return null
+	}
+
+	const filterParts: string[] = []
+	const segmentLabels: string[] = []
+
+	segments.forEach((segment, index) => {
+		const label = `trimmed_audio_${index}`
+		filterParts.push(
+			`[1:a]atrim=start=${formatFfmpegSeconds(segment.startMs)}:end=${formatFfmpegSeconds(segment.endMs)},asetpts=PTS-STARTPTS[${label}]`,
+		)
+		segmentLabels.push(`[${label}]`)
+	})
+
+	if (segmentLabels.length === 1) {
+		filterParts.push(`${segmentLabels[0]}anull[aout]`)
+	} else {
+		filterParts.push(`${segmentLabels.join('')}concat=n=${segmentLabels.length}:v=0:a=1[aout]`)
+	}
+
+	return filterParts.join(';')
+}
+
+export function getEditedAudioExtension(mimeType?: string | null): string {
+	if (!mimeType) {
+		return '.webm'
+	}
+
+	if (mimeType.includes('wav')) {
+		return '.wav'
+	}
+
+	if (mimeType.includes('mp4') || mimeType.includes('m4a')) {
+		return '.m4a'
+	}
+
+	if (mimeType.includes('ogg')) {
+		return '.ogg'
+	}
+
+	return '.webm'
+}