First release

node_modules/mux.js/es/tools/caption-packet-parser.js

@@ -0,0 +1,189 @@
+/**
+ * mux.js
+ *
+ * Copyright (c) Brightcove
+ * Licensed Apache-2.0 https://github.com/videojs/mux.js/blob/master/LICENSE
+ *
+ * Reads in-band caption information from a video elementary
+ * stream. Captions must follow the CEA-708 standard for injection
+ * into an MPEG-2 transport streams.
+ * @see https://en.wikipedia.org/wiki/CEA-708
+ * @see https://www.gpo.gov/fdsys/pkg/CFR-2007-title47-vol1/pdf/CFR-2007-title47-vol1-sec15-119.pdf
+ */
+'use strict'; // Supplemental enhancement information (SEI) NAL units have a
+// payload type field to indicate how they are to be
+// interpreted. CEAS-708 caption content is always transmitted with
+// payload type 0x04.
+
+var USER_DATA_REGISTERED_ITU_T_T35 = 4,
+    RBSP_TRAILING_BITS = 128;
+/**
+  * Parse a supplemental enhancement information (SEI) NAL unit.
+  * Stops parsing once a message of type ITU T T35 has been found.
+  *
+  * @param bytes {Uint8Array} the bytes of a SEI NAL unit
+  * @return {object} the parsed SEI payload
+  * @see Rec. ITU-T H.264, 7.3.2.3.1
+  */
+
+var parseSei = function parseSei(bytes) {
+  var i = 0,
+      result = {
+    payloadType: -1,
+    payloadSize: 0
+  },
+      payloadType = 0,
+      payloadSize = 0; // go through the sei_rbsp parsing each each individual sei_message
+
+  while (i < bytes.byteLength) {
+    // stop once we have hit the end of the sei_rbsp
+    if (bytes[i] === RBSP_TRAILING_BITS) {
+      break;
+    } // Parse payload type
+
+
+    while (bytes[i] === 0xFF) {
+      payloadType += 255;
+      i++;
+    }
+
+    payloadType += bytes[i++]; // Parse payload size
+
+    while (bytes[i] === 0xFF) {
+      payloadSize += 255;
+      i++;
+    }
+
+    payloadSize += bytes[i++]; // this sei_message is a 608/708 caption so save it and break
+    // there can only ever be one caption message in a frame's sei
+
+    if (!result.payload && payloadType === USER_DATA_REGISTERED_ITU_T_T35) {
+      var userIdentifier = String.fromCharCode(bytes[i + 3], bytes[i + 4], bytes[i + 5], bytes[i + 6]);
+
+      if (userIdentifier === 'GA94') {
+        result.payloadType = payloadType;
+        result.payloadSize = payloadSize;
+        result.payload = bytes.subarray(i, i + payloadSize);
+        break;
+      } else {
+        result.payload = void 0;
+      }
+    } // skip the payload and parse the next message
+
+
+    i += payloadSize;
+    payloadType = 0;
+    payloadSize = 0;
+  }
+
+  return result;
+}; // see ANSI/SCTE 128-1 (2013), section 8.1
+
+
+var parseUserData = function parseUserData(sei) {
+  // itu_t_t35_contry_code must be 181 (United States) for
+  // captions
+  if (sei.payload[0] !== 181) {
+    return null;
+  } // itu_t_t35_provider_code should be 49 (ATSC) for captions
+
+
+  if ((sei.payload[1] << 8 | sei.payload[2]) !== 49) {
+    return null;
+  } // the user_identifier should be "GA94" to indicate ATSC1 data
+
+
+  if (String.fromCharCode(sei.payload[3], sei.payload[4], sei.payload[5], sei.payload[6]) !== 'GA94') {
+    return null;
+  } // finally, user_data_type_code should be 0x03 for caption data
+
+
+  if (sei.payload[7] !== 0x03) {
+    return null;
+  } // return the user_data_type_structure and strip the trailing
+  // marker bits
+
+
+  return sei.payload.subarray(8, sei.payload.length - 1);
+}; // see CEA-708-D, section 4.4
+
+
+var parseCaptionPackets = function parseCaptionPackets(pts, userData) {
+  var results = [],
+      i,
+      count,
+      offset,
+      data; // if this is just filler, return immediately
+
+  if (!(userData[0] & 0x40)) {
+    return results;
+  } // parse out the cc_data_1 and cc_data_2 fields
+
+
+  count = userData[0] & 0x1f;
+
+  for (i = 0; i < count; i++) {
+    offset = i * 3;
+    data = {
+      type: userData[offset + 2] & 0x03,
+      pts: pts
+    }; // capture cc data when cc_valid is 1
+
+    if (userData[offset + 2] & 0x04) {
+      data.ccData = userData[offset + 3] << 8 | userData[offset + 4];
+      results.push(data);
+    }
+  }
+
+  return results;
+};
+
+var discardEmulationPreventionBytes = function discardEmulationPreventionBytes(data) {
+  var length = data.byteLength,
+      emulationPreventionBytesPositions = [],
+      i = 1,
+      newLength,
+      newData; // Find all `Emulation Prevention Bytes`
+
+  while (i < length - 2) {
+    if (data[i] === 0 && data[i + 1] === 0 && data[i + 2] === 0x03) {
+      emulationPreventionBytesPositions.push(i + 2);
+      i += 2;
+    } else {
+      i++;
+    }
+  } // If no Emulation Prevention Bytes were found just return the original
+  // array
+
+
+  if (emulationPreventionBytesPositions.length === 0) {
+    return data;
+  } // Create a new array to hold the NAL unit data
+
+
+  newLength = length - emulationPreventionBytesPositions.length;
+  newData = new Uint8Array(newLength);
+  var sourceIndex = 0;
+
+  for (i = 0; i < newLength; sourceIndex++, i++) {
+    if (sourceIndex === emulationPreventionBytesPositions[0]) {
+      // Skip this byte
+      sourceIndex++; // Remove this position index
+
+      emulationPreventionBytesPositions.shift();
+    }
+
+    newData[i] = data[sourceIndex];
+  }
+
+  return newData;
+}; // exports
+
+
+module.exports = {
+  parseSei: parseSei,
+  parseUserData: parseUserData,
+  parseCaptionPackets: parseCaptionPackets,
+  discardEmulationPreventionBytes: discardEmulationPreventionBytes,
+  USER_DATA_REGISTERED_ITU_T_T35: USER_DATA_REGISTERED_ITU_T_T35
+};