update for flac metadata on iphone/rpi

src/audioMetadata.ts

@@ -26,6 +26,8 @@ const AUDIO_METADATA_EXTENSIONS = new Set([
 
 let ffmpegInstance: FFmpeg | null = null
 let ffmpegLoadPromise: Promise<FFmpeg> | null = null
+let ffmpegOperationPromise: Promise<void> = Promise.resolve()
+let ffmpegTempFileCounter = 0
 
 function sanitizeExtension(extension?: string | null) {
   return (extension || '').trim().replace(/^\./, '').toLowerCase()
@@ -54,6 +56,17 @@ async function getFFmpeg() {
   }
 }
 
+function createTempFileStem() {
+  ffmpegTempFileCounter += 1
+  return `metadata-${Date.now()}-${ffmpegTempFileCounter}`
+}
+
+function queueFFmpegOperation<T>(operation: () => Promise<T>) {
+  const pending = ffmpegOperationPromise.then(operation, operation)
+  ffmpegOperationPromise = pending.then(() => undefined, () => undefined)
+  return pending
+}
+
 function buildMetadataArgs(metadata: AudioTagMetadata) {
   const args: string[] = []
   if (metadata.title) args.push('-metadata', `title=${metadata.title}`)
@@ -74,37 +87,42 @@ export function supportsContainerMetadataEmbedding(extension?: string | null, mi
 export async function embedContainerAudioMetadata(blob: Blob, extension: string | undefined, metadata: AudioTagMetadata) {
   if (!metadata.title && !metadata.artist && !metadata.album && !metadata.trackNumber) return blob
 
-  const normalizedExtension = sanitizeExtension(extension) || 'audio'
-  const ffmpeg = await getFFmpeg()
-  const { fetchFile } = await import('@ffmpeg/util')
-  const inputPath = `input.${normalizedExtension}`
-  const outputPath = `output.${normalizedExtension}`
+  return queueFFmpegOperation(async () => {
+    const normalizedExtension = sanitizeExtension(extension) || 'audio'
+    const ffmpeg = await getFFmpeg()
+    const { fetchFile } = await import('@ffmpeg/util')
+    const tempStem = createTempFileStem()
+    const inputPath = `${tempStem}-input.${normalizedExtension}`
+    const outputPath = `${tempStem}-output.${normalizedExtension}`
 
-  await ffmpeg.writeFile(inputPath, await fetchFile(blob))
+    await ffmpeg.writeFile(inputPath, await fetchFile(blob))
 
-  try {
-    const exitCode = await ffmpeg.exec([
-      '-i', inputPath,
-      '-map', '0',
-      '-map_metadata', '-1',
-      '-c', 'copy',
-      ...buildMetadataArgs(metadata),
-      outputPath,
-    ])
+    try {
+      const exitCode = await ffmpeg.exec([
+        '-nostdin',
+        '-y',
+        '-i', inputPath,
+        '-map', '0',
+        '-map_metadata', '-1',
+        '-c', 'copy',
+        ...buildMetadataArgs(metadata),
+        outputPath,
+      ])
 
-    if (exitCode !== 0) {
-      throw new Error(`FFmpeg metadata update failed (${exitCode})`)
+      if (exitCode !== 0) {
+        throw new Error(`FFmpeg metadata update failed (${exitCode})`)
+      }
+
+      const outputData = await ffmpeg.readFile(outputPath)
+      const outputBytes = outputData instanceof Uint8Array ? outputData : new Uint8Array(new TextEncoder().encode(String(outputData)))
+      const outputCopy = new Uint8Array(outputBytes.byteLength)
+      outputCopy.set(outputBytes)
+      return new Blob([outputCopy], { type: blob.type || 'application/octet-stream' })
+    } finally {
+      try { await ffmpeg.deleteFile(inputPath) } catch {}
+      try { await ffmpeg.deleteFile(outputPath) } catch {}
     }
-
-    const outputData = await ffmpeg.readFile(outputPath)
-    const outputBytes = outputData instanceof Uint8Array ? outputData : new Uint8Array(new TextEncoder().encode(String(outputData)))
-    const outputCopy = new Uint8Array(outputBytes.byteLength)
-    outputCopy.set(outputBytes)
-    return new Blob([outputCopy], { type: blob.type || 'application/octet-stream' })
-  } finally {
-    try { await ffmpeg.deleteFile(inputPath) } catch {}
-    try { await ffmpeg.deleteFile(outputPath) } catch {}
-  }
+  })
 }
 
 export type { AudioTagMetadata }