feat(ffmpeg): added tempo and playback timecode selection

OnkelTem · Apr 18, 2021 · bc77dd5 · bc77dd5
1 parent 668ed04
commit bc77dd5
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Showing 4 changed files with 72 additions and 7 deletions.
diff --git a/lib/audio.ts b/lib/audio.ts
@@ -87,16 +87,38 @@ export async function getOpusReader(
   };
 }
 
+// http://ffmpeg.org/ffmpeg-utils.html#Time-duration
+export type FFmpegDuration = string;
+
+const reFFmpegDuration = /^((\d{2}:)?\d{2}:\d{2}(\.\d+)?|\d+(\.\d+)?(s|ms|us)?)$/gm;
+
+function isFFmpegDuration(arg: string): arg is FFmpegDuration {
+  // Either [-][HH:]MM:SS[.m...] or [-]S+[.m...][s|ms|us]
+  return !!arg.match(reFFmpegDuration);
+}
+
+export type FFmpegTempo = number;
+
+function isFFmpegTempo(arg: number): arg is FFmpegTempo {
+  return arg >= 0.5 && arg <= 2.0;
+}
+
 export type FileStreamOptions = {
   samplingRate?: SamplingRate;
   volumeFactor?: number;
+  tempoFactor?: FFmpegTempo;
+  startAt?: FFmpegDuration | null;
+  endAt?: FFmpegDuration | null;
   ffmpegArgs?: FFmpegArgs;
 };
 
 const FILE_STREAM_DEFAULT_FFMPEG_ARGS: FFmpegArgs = ['-channel_layout', 'mono'];
 const FILE_STREAM_DEFAULT_OPTIONS: Required<FileStreamOptions> = {
   samplingRate: 48000,
   volumeFactor: 0.5,
+  tempoFactor: 1,
+  startAt: null,
+  endAt: null,
   ffmpegArgs: FILE_STREAM_DEFAULT_FFMPEG_ARGS,
 };
 
@@ -219,9 +241,34 @@ export function getAudioFileStream(path: string, parentLogger: Logger, options?:
 export function getAutoDecodeStream(stream: Readable, parentLogger: Logger, options?: FileStreamOptions): Duplex {
   const logger = parentLogger.child({ facility: 'getAutoDecodeStream' });
 
-  const { samplingRate, volumeFactor, ffmpegArgs }: Required<FileStreamOptions> =
+  const { samplingRate, volumeFactor, tempoFactor, startAt, endAt, ffmpegArgs }: Required<FileStreamOptions> =
     options != null ? { ...FILE_STREAM_DEFAULT_OPTIONS, ...options } : FILE_STREAM_DEFAULT_OPTIONS;
 
+  // From ... to ...
+  let startAtArg: [string, string] | [] = [];
+  let endAtArg: [string, string] | [] = [];
+  if (startAt != null) {
+    if (isFFmpegDuration(startAt)) {
+      startAtArg = ['-ss', startAt];
+    } else {
+      logger.warn(`Wrong startAt format: ${startAt}`);
+    }
+  }
+  if (endAt != null) {
+    if (isFFmpegDuration(endAt)) {
+      endAtArg = ['-t', endAt];
+    } else {
+      logger.warn(`Wrong endAt format: ${endAt}`);
+    }
+  }
+
+  const filters: string[] = [];
+  filters.push(`aresample=${samplingRate}`);
+  filters.push(`volume=${volumeFactor}`);
+  if (tempoFactor !== 1 && isFFmpegTempo(tempoFactor)) {
+    filters.push(`atempo=${tempoFactor}`);
+  }
+
   // Create transcoder stream
   const transcoderArguments = [
     '-analyzeduration',
@@ -230,10 +277,12 @@ export function getAutoDecodeStream(stream: Readable, parentLogger: Logger, opti
     '0',
     '-i',
     '-',
+    ...startAtArg,
+    ...endAtArg,
     '-f',
     's16le',
     '-filter:a',
-    `aresample=${samplingRate},volume=${volumeFactor}`,
+    filters.join(','),
     ...ffmpegArgs,
   ];
   const transcodeStream = new prism.FFmpeg({

diff --git a/lib/index.ts b/lib/index.ts
@@ -1,6 +1,7 @@
-export * from './zello';
 export { default } from './zello';
+export * from './zello';
 export * from './api';
 export * from './types';
 export * from './audio';
 export * from './utils';
+export * from './logger';
diff --git a/lib/logger.ts b/lib/logger.ts
@@ -1,8 +1,19 @@
 import { isEnvVar } from './utils';
-import { LoggerOptions } from 'pino';
+import { LoggerOptions as LoggerOptionsBase } from 'pino';
+
+export const loggerLevels = ['fatal', 'error', 'warn', 'info', 'debug', 'trace'] as const;
+export type LoggerLevel = typeof loggerLevels[number];
+
+export interface LoggerOptions extends Omit<LoggerOptionsBase, 'level'> {
+  level: LoggerLevel;
+}
+
+export function isLoggerLevel(arg?: string): arg is LoggerLevel {
+  return arg != null && loggerLevels.includes(arg as LoggerLevel);
+}
 
 export const DEFAULT_LOGGER_OPTIONS: LoggerOptions = {
-  level: process.env.LOGGER_LEVEL != null ? process.env.LOGGER_LEVEL : 'info',
+  level: isLoggerLevel(process.env.LOGGER_LEVEL) ? process.env.LOGGER_LEVEL : 'info',
   ...(isEnvVar(process.env.LOGGER_PRETTY) && {
     prettyPrint: {
       ignore: 'pid,hostname',

diff --git a/lib/types.ts b/lib/types.ts
@@ -174,8 +174,10 @@ type OpusInfo = {
   frameSize: number;
 };
 
-type SamplingRate = 8000 | 12000 | 16000 | 24000 | 48000;
-type FrameSize = 2.5 | 5 | 10 | 20 | 40 | 60;
+const samplingRates = [8000, 12000, 16000, 24000, 48000] as const;
+type SamplingRate = typeof samplingRates[number];
+const frameSizes = [2.5, 5, 10, 20, 40, 60] as const;
+type FrameSize = typeof frameSizes[number];
 type Channels = 1 | 2;
 
 type FFmpegArgs = string[];
@@ -214,8 +216,10 @@ export {
   StreamGetter,
   OpusInfo,
   DeferredPromise,
+  samplingRates,
   SamplingRate,
   FFmpegArgs,
+  frameSizes,
   FrameSize,
   Channels,
   StreamGetterOptions,