/*! @license
* Shaka Player
* Copyright 2016 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
goog.provide('shaka.transmuxer.Opus');
goog.requireType('shaka.util.TsParser');
/**
* Opus utils
*/
shaka.transmuxer.Opus = class {
/**
* @param {!shaka.util.TsParser.OpusMetadata} metadata
* @return {!Uint8Array}
*/
static getAudioConfig(metadata) {
let mapping = [];
switch (metadata.channelConfigCode) {
case 0x01:
case 0x02:
mapping = [0x0];
break;
case 0x00: // dualmono
mapping = [0xFF, 1, 1, 0, 1];
break;
case 0x80: // dualmono
mapping = [0xFF, 2, 0, 0, 1];
break;
case 0x03:
mapping = [0x01, 2, 1, 0, 2, 1];
break;
case 0x04:
mapping = [0x01, 2, 2, 0, 1, 2, 3];
break;
case 0x05:
mapping = [0x01, 3, 2, 0, 4, 1, 2, 3];
break;
case 0x06:
mapping = [0x01, 4, 2, 0, 4, 1, 2, 3, 5];
break;
case 0x07:
mapping = [0x01, 4, 2, 0, 4, 1, 2, 3, 5, 6];
break;
case 0x08:
mapping = [0x01, 5, 3, 0, 6, 1, 2, 3, 4, 5, 7];
break;
case 0x82:
mapping = [0x01, 1, 2, 0, 1];
break;
case 0x83:
mapping = [0x01, 1, 3, 0, 1, 2];
break;
case 0x84:
mapping = [0x01, 1, 4, 0, 1, 2, 3];
break;
case 0x85:
mapping = [0x01, 1, 5, 0, 1, 2, 3, 4];
break;
case 0x86:
mapping = [0x01, 1, 6, 0, 1, 2, 3, 4, 5];
break;
case 0x87:
mapping = [0x01, 1, 7, 0, 1, 2, 3, 4, 5, 6];
break;
case 0x88:
mapping = [0x01, 1, 8, 0, 1, 2, 3, 4, 5, 6, 7];
break;
}
return new Uint8Array([
0x00, // Version (1)
metadata.channelCount, // OutputChannelCount: 2
0x00, 0x00, // PreSkip: 2
(metadata.sampleRate >>> 24) & 0xFF, // Audio sample rate: 4
(metadata.sampleRate >>> 17) & 0xFF,
(metadata.sampleRate >>> 8) & 0xFF,
(metadata.sampleRate >>> 0) & 0xFF,
0x00, 0x00, // Global Gain : 2
...mapping,
]);
}
/**
* Returns the number of 48 kHz samples represented by an opus packet,
* derived from its TOC byte and (for code 3) the frame-count byte.
* See RFC 6716 §3.1.
*
* One PES packet in an MPEG-TS opus stream can carry a multi-frame opus
* packet (e.g. browser MediaRecorder emits code-3 packets with 3x 20ms
* CELT frames = 60ms per packet). Treating one PES packet as one frame's
* worth of samples under-counts duration and breaks timeline alignment
* in the resulting mp4.
*
* Returned counts are at 48 kHz. This assumes the caller writes the opus
* track with a 48 kHz mp4 timescale, which TsParser hardcodes for opus
* (RFC 6716: opus always decodes internally at 48 kHz; OpusHead's input
* sample rate is informational). If that hardcode ever becomes variable,
* scale the return value by (timescale / 48000).
*
* @param {!Uint8Array} packet Opus packet starting at the TOC byte.
* @return {number} Sample count at 48 kHz.
*/
static getPacketSampleCount(packet) {
if (packet.length < 1) {
return shaka.transmuxer.Opus.OPUS_AUDIO_SAMPLE_PER_FRAME;
}
const toc = packet[0];
const config = (toc >> 3) & 0x1F;
const code = toc & 0x03;
const spf = shaka.transmuxer.Opus.SAMPLES_PER_FRAME_BY_CONFIG_[config];
let frames;
if (code === 0) {
frames = 1;
} else if (code === 1 || code === 2) {
frames = 2;
} else {
// Code 3: number of frames is in bits 0-5 of the second byte.
if (packet.length < 2) {
return spf;
}
frames = packet[1] & 0x3F;
if (frames === 0) {
return spf;
}
}
return spf * frames;
}
};
/**
* Samples per opus frame at 48 kHz, indexed by the 5-bit config field from
* the TOC byte. See RFC 6716 §3.1, Table 2.
*
* @private @const {!Array<number>}
*/
shaka.transmuxer.Opus.SAMPLES_PER_FRAME_BY_CONFIG_ = [
480, 960, 1920, 2880, // SILK NB 10/20/40/60 ms
480, 960, 1920, 2880, // SILK MB 10/20/40/60 ms
480, 960, 1920, 2880, // SILK WB 10/20/40/60 ms
480, 960, // Hybrid SWB 10/20 ms
480, 960, // Hybrid FB 10/20 ms
120, 240, 480, 960, // CELT NB 2.5/5/10/20 ms
120, 240, 480, 960, // CELT WB
120, 240, 480, 960, // CELT SWB
120, 240, 480, 960, // CELT FB
];
/**
* Retained for backward compatibility. Prefer getPacketSampleCount(), which
* handles multi-frame opus packets correctly.
*
* @const {number}
*/
shaka.transmuxer.Opus.OPUS_AUDIO_SAMPLE_PER_FRAME = 960;