NodeAV

Appearance

node-av / lib / avGetCodecString

Function: avGetCodecString() ​

avGetCodecString(codecpar, frameRate?): string | null

Defined in: src/lib/utilities.ts:272

Get RFC 6381 codec string from codec parameters.

Generates codec strings for MPEG-DASH and HLS manifests following RFC 6381. Uses FFmpeg's centralized ff_make_codec_str() implementation (libavformat/codecstring.c).

Supported codecs:

  • WebM codecs: VP8, VP9 (with detailed profile/level), Vorbis, Opus, FLAC
  • H.264 (avc1): avc1.PPCCLL (profile, constraints, level)
  • HEVC (hvc1): hvc1.P.PC.TL.C (profile, profile_compatibility, tier+level, constraints)
  • AV1 (av01): av01.P.LLT.BB... (profile, level, tier, bitdepth, color info)
  • AAC: mp4a.40.AOT (audio object type)
  • MP2: mp4a.40.33
  • MP3: mp4a.40.34
  • AC-3: ac-3
  • E-AC-3: ec-3
  • MPEG-4 Visual: mp4v.20 (profile/level not implemented)

Parameters ​

codecpar ​

NativeWrapper<NativeCodecParameters>

Codec parameters

frameRate? ​

IRational

Optional frame rate for VP9 level calculation (only used for VP9)

Returns ​

string | null

RFC 6381 codec string, or null if codec not supported

Example ​

typescript
import { avGetCodecString } from 'node-av/lib';

// Get codec string for DASH/HLS manifest
const stream = output.video();
const codecString = avGetCodecString(stream.codecpar);
console.log(codecString); // "hvc1.1.6.L93.B0" for HEVC, "avc1.42c01e" for H.264

// VP9 with frame rate for accurate level
const codecStringVP9 = avGetCodecString(stream.codecpar, { num: 30, den: 1 });
console.log(codecStringVP9); // "vp09.00.30.08" - detailed VP9 string

// Use for DASH/HLS manifest
const mimeType = `video/mp4; codecs="${codecString}"`;

See ​

codecstring.c - FFmpeg implementation