@svta/common-media-library
Version:
A common library for media playback in JavaScript
78 lines • 2.59 kB
JavaScript
export function getSeiData(raw, startPos, endPos) {
const data = [];
for (let cursor = startPos; cursor < endPos; cursor++) {
if (cursor + 2 < endPos && raw.getUint8(cursor) === 0x00 && raw.getUint8(cursor + 1) === 0x00 && raw.getUint8(cursor + 2) === 0x03) {
data.push(0x00);
data.push(0x00);
cursor += 2;
}
else {
data.push(raw.getUint8(cursor));
}
}
return new DataView(new Uint8Array(data).buffer);
}
export function isCea608Sei(payloadType, payloadSize, sei, pos) {
if (payloadType !== 4 || payloadSize < 8) {
return false;
}
const countryCode = sei.getUint8(pos);
if (countryCode !== 0xB5) {
return false;
}
const providerCode = sei.getUint16(pos + 1);
if (providerCode !== 0x0031) {
return false;
}
const userIdentifier = sei.getUint32(pos + 3);
if (userIdentifier !== 0x47413934) {
return false;
}
const userDataTypeCode = sei.getUint8(pos + 7);
if (userDataTypeCode !== 0x03) {
return false;
}
return true;
}
export function isCCType(type) {
return type === 0 || type === 1;
}
export function isNonEmptyCCData(ccData1, ccData2) {
return (ccData1 & 0x7F) > 0 || (ccData2 & 0x7F) > 0;
}
export function isSeiNalUnitType(unitType) {
return unitType === 0x06;
}
export function parseCta608DataFromSei(sei, fieldData) {
let cursor = 0;
while (cursor < sei.byteLength) {
let payloadType = 0;
let payloadSize = 0;
let now;
do {
payloadType += now = sei.getUint8(cursor++);
} while (now === 0xFF);
do {
payloadSize += now = sei.getUint8(cursor++);
} while (now === 0xFF);
if (isCea608Sei(payloadType, payloadSize, sei, cursor)) {
const pos = cursor + 10;
const ccCount = pos + (sei.getUint8(pos - 2) & 0x1F) * 3;
for (let i = pos; i < ccCount; i += 3) {
const byte = sei.getUint8(i);
if (byte & 0x04) {
const ccType = byte & 0x03;
if (isCCType(ccType)) {
const ccData1 = sei.getUint8(i + 1);
const ccData2 = sei.getUint8(i + 2);
if (isNonEmptyCCData(ccData1, ccData2)) {
fieldData[ccType].push(ccData1, ccData2);
}
}
}
}
}
cursor += payloadSize;
}
}
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