diff --git a/README.md b/README.md
index c534a2b..472c931 100644
--- a/README.md
+++ b/README.md
@@ -29,6 +29,7 @@ Useful for reading codec parameters out of a `codecs=` string, checking support
 | EVC   | ✅ | ✅          |
 | L-HEVC | ✅ | ✅         |
 | MP4 (mp4a/mp4v — AAC, MP3, MPEG-4/2) | ✅ | ✅ |
+| AVS3 video/audio (avs3/av3a) | ✅ | ✅ |
 
 ## Install
 
@@ -97,8 +98,9 @@ console.log(info.toString());                // 'avc1.640028'
 
 - `codecInfoFactory(codecString)` — dispatches by prefix (`vp08`/`vp8`, `vp09`/`vp9`, `av01`,
   `avc1`/`avc2`/`avc3`/`avc4`, `hev1`/`hvc1`, `vvc1`/`vvi1`, `lvc1`, `apv1`, `evc1`, `lhv1`/`lhe1`,
-  `mp4a`/`mp4v`) and returns a `Vp8Info`, `Vp9Info`, `Av1Info`, `H264Info`, `H265Info`, `H266Info`,
-  `LcevcInfo`, `ApvInfo`, `EvcInfo`, `LhevcInfo`, or `Mp4Info`. Throws `Unknown codec` for anything else.
+  `mp4a`/`mp4v`, `avs3`, `av3a`) and returns a `Vp8Info`, `Vp9Info`, `Av1Info`, `H264Info`, `H265Info`,
+  `H266Info`, `LcevcInfo`, `ApvInfo`, `EvcInfo`, `LhevcInfo`, `Mp4Info`, `Avs3VideoInfo`, or
+  `Avs3AudioInfo`. Throws `Unknown codec` for anything else.
 - `vpx` — namespace exporting `Vp8Info`, `Vp9Info`, `vpxInfoFactory`, and the `Vpx*` enums.
 - `av1` — namespace exporting `Av1Info` and the `Av1*` enums.
 - `h264` — namespace exporting `H264Info`, `AvcProfileIdc`, and the `hProfile`/`hLevel` helpers.
@@ -119,6 +121,8 @@ console.log(info.toString());                // 'avc1.640028'
 - `mp4` — namespace exporting `Mp4Info` and the OTI helpers (`hObjectTypeIndication`,
   `hAudioObjectType`). Covers the RFC 6381 `mp4a`/`mp4v` ObjectTypeIndication scheme — AAC, MP3,
   MPEG-4 Visual, MPEG-2 video/audio and more (`mp4a.40.2`, `mp4a.69`, `mp4v.20.9`, …).
+- `avs3` — namespace exporting `Avs3VideoInfo` (`avs3.<profile>.<level>`) and `Avs3AudioInfo`
+  (`av3a.<codec_id>`) for the AVS3 video/audio standard.
 - Shared ISO/IEC 23001-8:2016 colour enums (`ColourPrimaries`, `TransferCharacteristics`,
   `MatrixCoefficients`, `VideoFullRangeFlag`) are re-exported from both namespaces.
 
diff --git a/src/codec/avs3/avs3-audio-info.spec.ts b/src/codec/avs3/avs3-audio-info.spec.ts
new file mode 100644
index 0000000..3ebb205
--- /dev/null
+++ b/src/codec/avs3/avs3-audio-info.spec.ts
@@ -0,0 +1,50 @@
+import {Avs3AudioInfo} from "./avs3-audio-info";
+
+describe('Avs3AudioInfo', () => {
+  describe('parse / round-trip', () => {
+    it.each(['av3a.00', 'av3a.01', 'av3a.02'])('parses and round-trips %s', (str) => {
+      expect(Avs3AudioInfo.fromString(str).toString()).toBe(str);
+    });
+
+    it('decodes the audio codec id', () => {
+      const info = Avs3AudioInfo.fromString('av3a.01');
+      expect(info.fourCC).toBe('av3a');
+      expect(info.audioCodecId).toBe(1);
+    });
+  });
+
+  describe('human-readable', () => {
+    it.each([
+      ['av3a.00', 'General Audio Coding'],
+      ['av3a.01', 'Lossless Audio Coding'],
+      ['av3a.02', 'Full Rate Audio Coding'],
+    ])('%s -> %s', (str, codec) => {
+      expect(Avs3AudioInfo.fromString(str).toHumanReadable().codec).toBe(codec);
+    });
+  });
+
+  describe('build', () => {
+    it('assembles a codec string from parts', () => {
+      const info = new Avs3AudioInfo();
+      info.audioCodecId = 2;
+      expect(info.toString()).toBe('av3a.02');
+    });
+
+    it('rejects out-of-range bytes', () => {
+      expect(() => { new Avs3AudioInfo().audioCodecId = 256; }).toThrow('audio_codec_id');
+    });
+  });
+
+  describe('invalid input', () => {
+    it.each(['av3a', 'av3a.00.01', 'av3a.GG'])(
+      'rejects malformed string %s',
+      (str) => {
+        expect(() => Avs3AudioInfo.fromString(str)).toThrow('Invalid AVS3 audio codec string');
+      },
+    );
+
+    it('rejects an unknown 4CC', () => {
+      expect(() => Avs3AudioInfo.fromString('av4a.00')).toThrow('Unknown codec');
+    });
+  });
+});
diff --git a/src/codec/avs3/avs3-audio-info.ts b/src/codec/avs3/avs3-audio-info.ts
new file mode 100644
index 0000000..d618abd
--- /dev/null
+++ b/src/codec/avs3/avs3-audio-info.ts
@@ -0,0 +1,64 @@
+import {CodecInfo} from "../codec-info";
+import {padStart} from "../pad-start";
+import {AVS3_AUDIO_FOUR_CCS, Avs3AudioFourCC, hAudioCodec} from "./enums";
+
+function assertByte(value: number, name: string): number {
+  if (!Number.isInteger(value) || value < 0 || value > 255) {
+    throw new Error(`${name} must be a byte in the range 0-255`);
+  }
+  return value;
+}
+
+// AVS3 audio codec information. Codec string: av3a.<audio_codec_id> (one hex byte).
+export class Avs3AudioInfo extends CodecInfo {
+  codecName = 'av3a';
+
+  private _fourCC: Avs3AudioFourCC = 'av3a';
+  private _audioCodecId = 0;
+
+  get fourCC(): Avs3AudioFourCC {
+    return this._fourCC;
+  }
+
+  set fourCC(fourCC: Avs3AudioFourCC) {
+    if (!AVS3_AUDIO_FOUR_CCS.includes(fourCC)) {
+      throw new Error(`Invalid AVS3 audio sample entry: ${fourCC}`);
+    }
+    this._fourCC = fourCC;
+  }
+
+  get audioCodecId(): number {
+    return this._audioCodecId;
+  }
+
+  set audioCodecId(audioCodecId: number) {
+    this._audioCodecId = assertByte(audioCodecId, 'audio_codec_id');
+  }
+
+  static fromString(codecString: string): Avs3AudioInfo {
+    const parts = codecString.split('.');
+    const fourCC = parts[0] as Avs3AudioFourCC;
+    if (!AVS3_AUDIO_FOUR_CCS.includes(fourCC)) {
+      throw new Error('Unknown codec');
+    }
+    if (parts.length !== 2 || !/^[0-9a-fA-F]{1,2}$/.test(parts[1])) {
+      throw new Error('Invalid AVS3 audio codec string, expected av3a.<audio_codec_id>');
+    }
+    const info = new Avs3AudioInfo();
+    info.fourCC = fourCC;
+    info.audioCodecId = parseInt(parts[1], 16);
+    return info;
+  }
+
+  toString(): string {
+    return `${this._fourCC}.${padStart(this._audioCodecId.toString(16), 2, '0')}`;
+  }
+
+  toHumanReadable() {
+    return {
+      fourCC: this._fourCC,
+      codec: hAudioCodec(this._audioCodecId),
+      audioCodecId: this._audioCodecId,
+    } as const;
+  }
+}
diff --git a/src/codec/avs3/avs3-video-info.spec.ts b/src/codec/avs3/avs3-video-info.spec.ts
new file mode 100644
index 0000000..b8b1ce2
--- /dev/null
+++ b/src/codec/avs3/avs3-video-info.spec.ts
@@ -0,0 +1,65 @@
+import {Avs3VideoInfo} from "./avs3-video-info";
+
+describe('Avs3VideoInfo', () => {
+  describe('parse / round-trip', () => {
+    it.each([
+      'avs3.20.10',
+      'avs3.32.50',
+      'avs3.22.20',
+      'avs3.ab.cd',
+    ])('parses and round-trips %s', (str) => {
+      expect(Avs3VideoInfo.fromString(str).toString()).toBe(str);
+    });
+
+    it('decodes the fields', () => {
+      const info = Avs3VideoInfo.fromString('avs3.20.10');
+      expect(info.fourCC).toBe('avs3');
+      expect(info.profileId).toBe(0x20);
+      expect(info.levelId).toBe(0x10);
+    });
+
+    it('normalizes hex to lowercase', () => {
+      expect(Avs3VideoInfo.fromString('avs3.AB.CD').toString()).toBe('avs3.ab.cd');
+    });
+  });
+
+  describe('human-readable', () => {
+    it.each([
+      ['avs3.20.10', 'Main 8-bit', '2.0.15'],
+      ['avs3.22.20', 'Main 10-bit', '4.0.30'],
+      ['avs3.30.50', 'High 8-bit', '8.0.30'],
+      ['avs3.32.50', 'High 10-bit', '8.0.30'],
+    ])('%s -> %s / level %s', (str, profile, level) => {
+      const hr = Avs3VideoInfo.fromString(str).toHumanReadable();
+      expect(hr.profile).toBe(profile);
+      expect(hr.level).toBe(level);
+    });
+  });
+
+  describe('build', () => {
+    it('assembles a codec string from parts', () => {
+      const info = new Avs3VideoInfo();
+      info.profileId = 0x20;
+      info.levelId = 0x10;
+      expect(info.toString()).toBe('avs3.20.10');
+    });
+
+    it('rejects out-of-range bytes', () => {
+      expect(() => { new Avs3VideoInfo().profileId = 256; }).toThrow('profile_id');
+      expect(() => { new Avs3VideoInfo().levelId = -1; }).toThrow('level_id');
+    });
+  });
+
+  describe('invalid input', () => {
+    it.each(['avs3', 'avs3.20', 'avs3.20.10.5', 'avs3.GG.10'])(
+      'rejects malformed string %s',
+      (str) => {
+        expect(() => Avs3VideoInfo.fromString(str)).toThrow('Invalid AVS3 video codec string');
+      },
+    );
+
+    it('rejects an unknown 4CC', () => {
+      expect(() => Avs3VideoInfo.fromString('avs2.20.10')).toThrow('Unknown codec');
+    });
+  });
+});
diff --git a/src/codec/avs3/avs3-video-info.ts b/src/codec/avs3/avs3-video-info.ts
new file mode 100644
index 0000000..d25e209
--- /dev/null
+++ b/src/codec/avs3/avs3-video-info.ts
@@ -0,0 +1,77 @@
+import {CodecInfo} from "../codec-info";
+import {padStart} from "../pad-start";
+import {AVS3_VIDEO_FOUR_CCS, Avs3VideoFourCC, hVideoLevel, hVideoProfile} from "./enums";
+
+function assertByte(value: number, name: string): number {
+  if (!Number.isInteger(value) || value < 0 || value > 255) {
+    throw new Error(`${name} must be a byte in the range 0-255`);
+  }
+  return value;
+}
+
+// AVS3 video codec information. Codec string: avs3.<profile_id>.<level_id> (two hex bytes).
+export class Avs3VideoInfo extends CodecInfo {
+  codecName = 'avs3';
+
+  private _fourCC: Avs3VideoFourCC = 'avs3';
+  private _profileId = 0;
+  private _levelId = 0;
+
+  get fourCC(): Avs3VideoFourCC {
+    return this._fourCC;
+  }
+
+  set fourCC(fourCC: Avs3VideoFourCC) {
+    if (!AVS3_VIDEO_FOUR_CCS.includes(fourCC)) {
+      throw new Error(`Invalid AVS3 video sample entry: ${fourCC}`);
+    }
+    this._fourCC = fourCC;
+  }
+
+  get profileId(): number {
+    return this._profileId;
+  }
+
+  set profileId(profileId: number) {
+    this._profileId = assertByte(profileId, 'profile_id');
+  }
+
+  get levelId(): number {
+    return this._levelId;
+  }
+
+  set levelId(levelId: number) {
+    this._levelId = assertByte(levelId, 'level_id');
+  }
+
+  static fromString(codecString: string): Avs3VideoInfo {
+    const parts = codecString.split('.');
+    const fourCC = parts[0] as Avs3VideoFourCC;
+    if (!AVS3_VIDEO_FOUR_CCS.includes(fourCC)) {
+      throw new Error('Unknown codec');
+    }
+    if (parts.length !== 3 || !/^[0-9a-fA-F]{1,2}$/.test(parts[1]) || !/^[0-9a-fA-F]{1,2}$/.test(parts[2])) {
+      throw new Error('Invalid AVS3 video codec string, expected avs3.<profile_id>.<level_id>');
+    }
+    const info = new Avs3VideoInfo();
+    info.fourCC = fourCC;
+    info.profileId = parseInt(parts[1], 16);
+    info.levelId = parseInt(parts[2], 16);
+    return info;
+  }
+
+  toString(): string {
+    const hex = (value: number) => padStart(value.toString(16), 2, '0');
+    return `${this._fourCC}.${hex(this._profileId)}.${hex(this._levelId)}`;
+  }
+
+  toHumanReadable() {
+    return {
+      fourCC: this._fourCC,
+      profile: hVideoProfile(this._profileId),
+      profileId: this._profileId,
+      level: hVideoLevel(this._levelId),
+      levelId: this._levelId,
+    } as const;
+  }
+}
diff --git a/src/codec/avs3/enums.ts b/src/codec/avs3/enums.ts
new file mode 100644
index 0000000..838ac3e
--- /dev/null
+++ b/src/codec/avs3/enums.ts
@@ -0,0 +1,38 @@
+// AVS3 (China AVS working group). Codec strings:
+//   avs3.<profile_id>.<level_id>   (video, hex bytes) e.g. avs3.20.10, avs3.32.50
+//   av3a.<audio_codec_id>          (audio, hex byte)  e.g. av3a.00
+
+export type Avs3VideoFourCC = 'avs3';
+export const AVS3_VIDEO_FOUR_CCS: readonly Avs3VideoFourCC[] = ['avs3'];
+
+export type Avs3AudioFourCC = 'av3a';
+export const AVS3_AUDIO_FOUR_CCS: readonly Avs3AudioFourCC[] = ['av3a'];
+
+export function hVideoProfile(profileId: number): string {
+  switch (profileId) {
+    case 0x20: return 'Main 8-bit';
+    case 0x22: return 'Main 10-bit';
+    case 0x30: return 'High 8-bit';
+    case 0x32: return 'High 10-bit';
+    default: return 'unknown';
+  }
+}
+
+// Only the level_id values with a confirmed mapping are named; others are reported by raw levelId.
+export function hVideoLevel(levelId: number): string {
+  switch (levelId) {
+    case 0x10: return '2.0.15';
+    case 0x20: return '4.0.30';
+    case 0x50: return '8.0.30';
+    default: return 'unknown';
+  }
+}
+
+export function hAudioCodec(audioCodecId: number): string {
+  switch (audioCodecId) {
+    case 0x00: return 'General Audio Coding';
+    case 0x01: return 'Lossless Audio Coding';
+    case 0x02: return 'Full Rate Audio Coding';
+    default: return 'unknown';
+  }
+}
diff --git a/src/codec/avs3/index.ts b/src/codec/avs3/index.ts
new file mode 100644
index 0000000..458845f
--- /dev/null
+++ b/src/codec/avs3/index.ts
@@ -0,0 +1,10 @@
+export {
+  AVS3_VIDEO_FOUR_CCS,
+  AVS3_AUDIO_FOUR_CCS,
+  hVideoProfile,
+  hVideoLevel,
+  hAudioCodec,
+} from './enums';
+export type {Avs3VideoFourCC, Avs3AudioFourCC} from './enums';
+export * from './avs3-video-info';
+export * from './avs3-audio-info';
diff --git a/src/index.spec.ts b/src/index.spec.ts
index 47849e1..62ecefa 100644
--- a/src/index.spec.ts
+++ b/src/index.spec.ts
@@ -1,4 +1,4 @@
-import {codecInfoFactory, version, vpx, av1, h264, h265, h266, lcevc, apv, evc, lhevc, mp4} from './index';
+import {codecInfoFactory, version, vpx, av1, h264, h265, h266, lcevc, apv, evc, lhevc, mp4, avs3} from './index';
 
 describe('codecInfoFactory', () => {
   it('dispatches vp8 strings to Vp8Info', () => {
@@ -79,6 +79,19 @@ describe('codecInfoFactory', () => {
     expect(video.codecName).toBe('mp4v');
   });
 
+  it('dispatches avs3 strings to Avs3VideoInfo', () => {
+    const info = codecInfoFactory('avs3.20.10');
+    expect(info).toBeInstanceOf(avs3.Avs3VideoInfo);
+    expect(info.codecName).toBe('avs3');
+    expect((info as avs3.Avs3VideoInfo).profileId).toBe(0x20);
+  });
+
+  it('dispatches av3a strings to Avs3AudioInfo', () => {
+    const info = codecInfoFactory('av3a.01');
+    expect(info).toBeInstanceOf(avs3.Avs3AudioInfo);
+    expect(info.codecName).toBe('av3a');
+  });
+
   it('throws on an unknown codec', () => {
     expect(() => codecInfoFactory('theora')).toThrow('Unknown codec');
     expect(() => codecInfoFactory('tx3g')).toThrow('Unknown codec');
diff --git a/src/index.ts b/src/index.ts
index 6401c61..a984c2a 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -8,6 +8,7 @@ import {ApvInfo} from "./codec/apv";
 import {EvcInfo} from "./codec/evc";
 import {LhevcInfo} from "./codec/lhevc";
 import {Mp4Info} from "./codec/mp4";
+import {Avs3VideoInfo, Avs3AudioInfo} from "./codec/avs3";
 
 export * as vpx from "./codec/vpx";
 export * as av1 from "./codec/av1";
@@ -19,6 +20,7 @@ export * as apv from "./codec/apv";
 export * as evc from "./codec/evc";
 export * as lhevc from "./codec/lhevc";
 export * as mp4 from "./codec/mp4";
+export * as avs3 from "./codec/avs3";
 export * from './codec/codec-info';
 
 export const version = '__lib_version__'; // Version will be injected on the build
@@ -54,5 +56,11 @@ export const codecInfoFactory = (codecString: string) => {
   if (codecString.startsWith('mp4a') || codecString.startsWith('mp4v')) {
     return Mp4Info.fromString(codecString);
   }
+  if (codecString.startsWith('avs3')) {
+    return Avs3VideoInfo.fromString(codecString);
+  }
+  if (codecString.startsWith('av3a')) {
+    return Avs3AudioInfo.fromString(codecString);
+  }
   throw new Error('Unknown codec');
 }
\ No newline at end of file