#782 Support Adaptive Multi-Rate (AMR) audio codec

README.md

@@ -48,6 +48,7 @@ If you find this project useful and would like to support its development, consi
 | ------------- |---------------------------------| -------------------------------------------------------------------|:---------------------------------------------------------------------------------------------------------------------------------------------:|
 | AIFF / AIFF-C | Audio Interchange File Format   | [:link:](https://wikipedia.org/wiki/Audio_Interchange_File_Format) | <img src="https://upload.wikimedia.org/wikipedia/commons/8/84/Apple_Computer_Logo_rainbow.svg" width="40" alt="Apple rainbow logo">           |
 | AAC           | ADTS / Advanced Audio Coding    | [:link:](https://en.wikipedia.org/wiki/Advanced_Audio_Coding)      | <img src="https://svgshare.com/i/UT8.svg" width="40" alt="AAC logo">                                                                          |
+| AMR           | Adaptive Multi-Rate audio codec | [:link:](https://en.wikipedia.org/wiki/Adaptive_Multi-Rate_audio_codec) | <img src="https://foreverhits.files.wordpress.com/2015/05/ape_audio.jpg" width="40" alt="Monkey's Audio logo">                           |
 | APE           | Monkey's Audio                  | [:link:](https://wikipedia.org/wiki/Monkey's_Audio)                | <img src="https://foreverhits.files.wordpress.com/2015/05/ape_audio.jpg" width="40" alt="Monkey's Audio logo">                                |
 | ASF           | Advanced Systems Format         | [:link:](https://wikipedia.org/wiki/Advanced_Systems_Format)       |                                                                                                                                               |
 | BWF           | Broadcast Wave Format           | [:link:](https://en.wikipedia.org/wiki/Broadcast_Wave_Format)      |                                                                                                                                               |

lib/ParserFactory.ts

@@ -21,6 +21,7 @@ import { musepackParserLoader } from './musepack/MusepackLoader.js';
 import { oggParserLoader } from './ogg/OggLoader.js';
 import { wavpackParserLoader } from './wavpack/WavPackLoader.js';
 import { riffParserLoader } from './wav/WaveLoader.js';
+import { amrParserLoader } from './amr/AmrLoader.js';
 
 const debug = initDebug('music-metadata:parser:factory');
 
@@ -81,7 +82,8 @@ export class ParserFactory {
       wavpackParserLoader,
       musepackParserLoader,
       dsfParserLoader,
-      dsdiffParserLoader
+      dsdiffParserLoader,
+      amrParserLoader
     ].forEach(parser => this.registerParser(parser));
   }
 
@@ -220,6 +222,9 @@ function getParserIdForMimeType(httpContentType: string | undefined): ParserType
 
         case 'dsf':
           return 'dsf';
+
+        case 'amr':
+          return 'amr';
       }
       break;
 

lib/amr/AmrLoader.ts

@@ -0,0 +1,12 @@
+import type { IParserLoader, ITokenParser } from '../ParserFactory.js';
+import type { INativeMetadataCollector } from '../common/MetadataCollector.js';
+import type { ITokenizer } from 'strtok3';
+import type { IOptions } from '../type.js';
+
+export const amrParserLoader: IParserLoader = {
+  parserType: 'amr',
+  extensions: ['.amr'],
+  async load(metadata: INativeMetadataCollector, tokenizer: ITokenizer, options: IOptions): Promise<ITokenParser> {
+    return new (await import('./AmrParser.js')).AmrParser(metadata, tokenizer, options);
+  }
+};

lib/amr/AmrParser.ts

@@ -0,0 +1,57 @@
+import { BasicParser } from '../common/BasicParser.js';
+import { AnsiStringType } from 'token-types';
+import initDebug from 'debug';
+import { FrameHeader } from './AmrToken.js';
+
+const debug = initDebug('music-metadata:parser:AMR');
+
+/**
+ * There are 8 varying levels of compression. First byte of the frame specifies CMR
+ * (codec mode request), values 0-7 are valid for AMR. Each mode have different frame size.
+ * This table reflects that fact.
+ */
+const m_block_size = [12, 13, 15, 17, 19, 20, 26, 31, 5, 0, 0, 0, 0, 0, 0, 0];
+
+/**
+ * Adaptive Multi-Rate audio codec
+ */
+export class AmrParser extends BasicParser {
+
+  public async parse(): Promise<void> {
+    const magicNr = await this.tokenizer.readToken(new AnsiStringType(5));
+    if (magicNr !== '#!AMR') {
+      throw new Error('Invalid AMR file: invalid MAGIC number');
+    }
+    this.metadata.setFormat('container', 'AMR');
+    this.metadata.setFormat('codec', 'AMR');
+    this.metadata.setFormat('sampleRate', 8000);
+    this.metadata.setFormat('bitrate', 64000);
+    this.metadata.setFormat('numberOfChannels', 1);
+
+    let total_size = 0;
+    let frames = 0;
+
+    const assumedFileLength = this.tokenizer.fileInfo?.size ?? Number.MAX_SAFE_INTEGER;
+
+    if (this.options.duration) {
+      while (this.tokenizer.position < assumedFileLength) {
+
+        const header = await this.tokenizer.readToken(FrameHeader);
+
+        /* first byte is rate mode. each rate mode has frame of given length. look it up. */
+        const size = m_block_size[header.frameType];
+
+        if(size>0) {
+          total_size += size + 1;
+          if (total_size > assumedFileLength) break;
+          await this.tokenizer.ignore(size);
+          ++frames;
+        } else {
+          debug(`Found no-data frame, frame-type: ${header.frameType}. Skipping`);
+        }
+
+      }
+      this.metadata.setFormat('duration', frames * 0.02);
+    }
+  }
+}

lib/amr/AmrToken.ts

@@ -0,0 +1,21 @@
+import type { IGetToken } from 'strtok3';
+import { getBitAllignedNumber } from '../common/Util.js';
+
+interface IFrameHeader {
+  frameType: number;
+}
+
+/**
+ * ID3v2 header
+ * Ref: http://id3.org/id3v2.3.0#ID3v2_header
+ * ToDo
+ */
+export const FrameHeader: IGetToken<IFrameHeader > = {
+  len: 1,
+
+  get: (buf: Uint8Array, off: number): IFrameHeader => {
+    return {
+      frameType: getBitAllignedNumber(buf, off, 1, 4)
+    };
+  }
+};

lib/type.ts

@@ -596,7 +596,8 @@ export type ParserType =
   | 'dsf'
   | 'dsdiff'
   | 'adts'
-  | 'matroska';
+  | 'matroska'
+  | 'amr';
 
 export interface IOptions {
 

test/test-file-amr.ts

@@ -0,0 +1,42 @@
+import { assert } from 'chai';
+import path from 'node:path';
+import { Parsers } from './metadata-parsers.js';
+import { samplePath } from './util.js';
+
+const amrPath = path.join(samplePath, 'amr');
+
+describe('Adaptive Multi-Rate (AMR) audio file', () => {
+
+  Parsers.forEach(parser => {
+
+    describe('parser.description', () => {
+
+      it('parse: sample.amr', async function () {
+        const  {format} = await parser.initParser(() => this.skip(), path.join(amrPath, 'sample.amr'), 'audio/amr', {duration: true});
+        assert.strictEqual(format.sampleRate, 8000, 'format.sampleRate');
+        assert.strictEqual(format.numberOfChannels, 1, 'format.numberOfChannels');
+        assert.strictEqual(format.bitrate, 64000, 'format.bitrate');
+        assert.approximately(format.duration, 35.36, 0.0005, 'format.duration');
+      });
+
+      it('parse: gs-16b-1c-8000hz.amr', async function () {
+        const {format} = await parser.initParser(() => this.skip(), path.join(amrPath, 'gs-16b-1c-8000hz.amr'), 'audio/amr', {duration: true});
+        assert.strictEqual(format.sampleRate, 8000, 'format.sampleRate');
+        assert.strictEqual(format.numberOfChannels, 1, 'format.numberOfChannels');
+        assert.strictEqual(format.bitrate, 64000, 'format.bitrate');
+        assert.approximately(format.duration, 16.42, 0.0005, 'format.duration');
+      });
+
+
+      it('parse: ff-16b-1c-8000hz.amr', async function () {
+        const {format} = await parser.initParser(() => this.skip(), path.join(amrPath, 'ff-16b-1c-8000hz.amr'), 'audio/amr', {duration: true});
+        assert.strictEqual(format.sampleRate, 8000, 'format.sampleRate');
+        assert.strictEqual(format.numberOfChannels, 1, 'format.numberOfChannels');
+        assert.strictEqual(format.bitrate, 64000, 'format.bitrate');
+        assert.approximately(format.duration, 187.56, 0.0005, 'format.duration');
+      });
+
+    });
+  });
+
+});