mux.js - npm Package Compare versions

Comparing version 5.3.1 to 5.4.0

lib/mp4/probe.js

@@ -13,59 +13,6 @@ /**
 var toHexString = require('../utils/bin').toHexString;
-var findBox, parseType, timescale, startTime, getVideoTrackIds, getTracks;
+var mp4Inspector = require('../tools/mp4-inspector.js');
+var timescale, startTime, compositionStartTime, getVideoTrackIds, getTracks;
 
-// Find the data for a box specified by its path
-findBox = function(data, path) {
-  var results = [],
-      i, size, type, end, subresults;
-
-  if (!path.length) {
-    // short-circuit the search for empty paths
-    return null;
-  }
-
-  for (i = 0; i < data.byteLength;) {
-    size  = toUnsigned(data[i]     << 24 |
-                       data[i + 1] << 16 |
-                       data[i + 2] <<  8 |
-                       data[i + 3]);
-
-    type = parseType(data.subarray(i + 4, i + 8));
-
-    end = size > 1 ? i + size : data.byteLength;
-
-    if (type === path[0]) {
-      if (path.length === 1) {
-        // this is the end of the path and we've found the box we were
-        // looking for
-        results.push(data.subarray(i + 8, end));
-      } else {
-        // recursively search for the next box along the path
-        subresults = findBox(data.subarray(i + 8, end), path.slice(1));
-        if (subresults.length) {
-          results = results.concat(subresults);
-        }
-      }
-    }
-    i = end;
-  }
-
-  // we've finished searching all of data
-  return results;
-};
-
 /**
- * Returns the string representation of an ASCII encoded four byte buffer.
- * @param buffer {Uint8Array} a four-byte buffer to translate
- * @return {string} the corresponding string
- */
-parseType = function(buffer) {
-  var result = '';
-  result += String.fromCharCode(buffer[0]);
-  result += String.fromCharCode(buffer[1]);
-  result += String.fromCharCode(buffer[2]);
-  result += String.fromCharCode(buffer[3]);
-  return result;
-};
-
-/**
  * Parses an MP4 initialization segment and extracts the timescale
@@ -91,3 +38,3 @@ * values for any declared tracks. Timescale values indicate the
     result = {},
-    traks = findBox(init, ['moov', 'trak']);
+    traks = mp4Inspector.findBox(init, ['moov', 'trak']);
 
@@ -98,3 +45,3 @@ // mdhd timescale
 
-    tkhd = findBox(trak, ['tkhd'])[0];
+    tkhd = mp4Inspector.findBox(trak, ['tkhd'])[0];
     if (!tkhd) {
@@ -110,3 +57,3 @@ return null;
 
-    mdhd = findBox(trak, ['mdia', 'mdhd'])[0];
+    mdhd = mp4Inspector.findBox(trak, ['mdia', 'mdhd'])[0];
     if (!mdhd) {
@@ -145,7 +92,7 @@ return null;
   // we need info from two childrend of each track fragment box
-  trafs = findBox(fragment, ['moof', 'traf']);
+  trafs = mp4Inspector.findBox(fragment, ['moof', 'traf']);
 
   // determine the start times for each track
   baseTimes = [].concat.apply([], trafs.map(function(traf) {
-    return findBox(traf, ['tfhd']).map(function(tfhd) {
+    return mp4Inspector.findBox(traf, ['tfhd']).map(function(tfhd) {
       var id, scale, baseTime;
@@ -162,3 +109,3 @@
       // get the base media decode time from the tfdt
-      baseTime = findBox(traf, ['tfdt']).map(function(tfdt) {
+      baseTime = mp4Inspector.findBox(traf, ['tfdt']).map(function(tfdt) {
         var version, result;
@@ -193,2 +140,52 @@
 /**
+ * Determine the composition start, in seconds, for an MP4
+ * fragment.
+ *
+ * The composition start time of a fragment can be calculated using the base
+ * media decode time, composition time offset, and timescale, as follows:
+ *
+ * compositionStartTime = (baseMediaDecodeTime + compositionTimeOffset) / timescale
+ *
+ * All of the aforementioned information is contained within a media fragment's
+ * `traf` box, except for timescale info, which comes from the initialization
+ * segment, so a track id (also contained within a `traf`) is also necessary to
+ * associate it with a timescale
+ *
+ *
+ * @param timescales {object} - a hash of track ids to timescale values.
+ * @param fragment {Unit8Array} - the bytes of a media segment
+ * @return {number} the composition start time for the fragment, in seconds
+ **/
+compositionStartTime = function(timescales, fragment) {
+  var trafBoxes = mp4Inspector.findBox(fragment, ['moof', 'traf']);
+  var baseMediaDecodeTime = 0;
+  var compositionTimeOffset = 0;
+  var trackId;
+
+  if (trafBoxes && trafBoxes.length) {
+    // The spec states that track run samples contained within a `traf` box are contiguous, but
+    // it does not explicitly state whether the `traf` boxes themselves are contiguous.
+    // We will assume that they are, so we only need the first to calculate start time.
+    var parsedTraf = mp4Inspector.parseTraf(trafBoxes[0]);
+
+    for (var i = 0; i < parsedTraf.boxes.length; i++) {
+      if (parsedTraf.boxes[i].type === 'tfhd') {
+        trackId = parsedTraf.boxes[i].trackId;
+      } else if (parsedTraf.boxes[i].type === 'tfdt') {
+        baseMediaDecodeTime = parsedTraf.boxes[i].baseMediaDecodeTime;
+      } else if (parsedTraf.boxes[i].type === 'trun' && parsedTraf.boxes[i].samples.length) {
+        compositionTimeOffset = parsedTraf.boxes[i].samples[0].compositionTimeOffset || 0;
+      }
+    }
+  }
+
+  // Get timescale for this specific track. Assume a 90kHz clock if no timescale was
+  // specified.
+  var timescale = timescales[trackId] || 90e3;
+
+  // return the composition start time, in seconds
+  return (baseMediaDecodeTime + compositionTimeOffset) / timescale;
+};
+
+/**
   * Find the trackIds of the video tracks in this source.
@@ -205,11 +202,11 @@ * Found by parsing the Handler Reference and Track Header Boxes:
 getVideoTrackIds = function(init) {
-  var traks = findBox(init, ['moov', 'trak']);
+  var traks = mp4Inspector.findBox(init, ['moov', 'trak']);
   var videoTrackIds = [];
 
   traks.forEach(function(trak) {
-    var hdlrs = findBox(trak, ['mdia', 'hdlr']);
-    var tkhds = findBox(trak, ['tkhd']);
+    var hdlrs = mp4Inspector.findBox(trak, ['mdia', 'hdlr']);
+    var tkhds = mp4Inspector.findBox(trak, ['tkhd']);
 
     hdlrs.forEach(function(hdlr, index) {
-      var handlerType = parseType(hdlr.subarray(8, 12));
+      var handlerType = mp4Inspector.parseType(hdlr.subarray(8, 12));
       var tkhd = tkhds[index];
@@ -238,3 +235,3 @@ var view;
 getTracks = function(init) {
-  var traks = findBox(init, ['moov', 'trak']);
+  var traks = mp4Inspector.findBox(init, ['moov', 'trak']);
   var tracks = [];
@@ -244,3 +241,3 @@
     var track = {};
-    var tkhd = findBox(trak, ['tkhd'])[0];
+    var tkhd = mp4Inspector.findBox(trak, ['tkhd'])[0];
     var view, version;
@@ -256,7 +253,7 @@
 
-    var hdlr = findBox(trak, ['mdia', 'hdlr'])[0];
+    var hdlr = mp4Inspector.findBox(trak, ['mdia', 'hdlr'])[0];
 
     // type
     if (hdlr) {
-      var type = parseType(hdlr.subarray(8, 12));
+      var type = mp4Inspector.parseType(hdlr.subarray(8, 12));
 
@@ -274,3 +271,3 @@ if (type === 'vide') {
     // codec
-    var stsd = findBox(trak, ['mdia', 'minf', 'stbl', 'stsd'])[0];
+    var stsd = mp4Inspector.findBox(trak, ['mdia', 'minf', 'stbl', 'stsd'])[0];
 
@@ -280,5 +277,5 @@ if (stsd) {
       // gives the codec type string
-      track.codec = parseType(sampleDescriptions.subarray(4, 8));
+      track.codec = mp4Inspector.parseType(sampleDescriptions.subarray(4, 8));
 
-      var codecBox = findBox(sampleDescriptions, [track.codec])[0];
+      var codecBox = mp4Inspector.findBox(sampleDescriptions, [track.codec])[0];
       var codecConfig, codecConfigType;
@@ -292,3 +289,3 @@
           codecConfig = codecBox.subarray(78);
-          codecConfigType = parseType(codecConfig.subarray(4, 8));
+          codecConfigType = mp4Inspector.parseType(codecConfig.subarray(4, 8));
 
@@ -313,3 +310,3 @@ if (codecConfigType === 'avcC' && codecConfig.length > 11) {
           codecConfig = codecBox.subarray(28);
-          codecConfigType = parseType(codecConfig.subarray(4, 8));
+          codecConfigType = mp4Inspector.parseType(codecConfig.subarray(4, 8));
 
@@ -331,3 +328,3 @@ if (codecConfigType === 'esds' && codecConfig.length > 20 && codecConfig[19] !== 0) {
 
-    var mdhd = findBox(trak, ['mdia', 'mdhd'])[0];
+    var mdhd = mp4Inspector.findBox(trak, ['mdia', 'mdhd'])[0];
 
@@ -350,8 +347,10 @@ if (mdhd && tkhd) {
 module.exports = {
-  findBox: findBox,
-  parseType: parseType,
+  // export mp4 inspector's findBox and parseType for backwards compatibility
+  findBox: mp4Inspector.findBox,
+  parseType: mp4Inspector.parseType,
   timescale: timescale,
   startTime: startTime,
+  compositionStartTime: compositionStartTime,
   videoTrackIds: getVideoTrackIds,
   tracks: getTracks
 };

lib/tools/mp4-inspector.js

@@ -15,4 +15,2 @@ /**
   textifyMp4,
-
-  parseType = require('../mp4/probe').parseType,
   toUnsigned = require('../utils/bin').toUnsigned,
@@ -33,2 +31,54 @@ parseMp4Date = function(seconds) {
   },
+  /**
+   * Returns the string representation of an ASCII encoded four byte buffer.
+   * @param buffer {Uint8Array} a four-byte buffer to translate
+   * @return {string} the corresponding string
+   */
+  parseType = function(buffer) {
+    var result = '';
+    result += String.fromCharCode(buffer[0]);
+    result += String.fromCharCode(buffer[1]);
+    result += String.fromCharCode(buffer[2]);
+    result += String.fromCharCode(buffer[3]);
+    return result;
+  },
+  // Find the data for a box specified by its path
+  findBox = function(data, path) {
+    var results = [],
+        i, size, type, end, subresults;
+
+    if (!path.length) {
+      // short-circuit the search for empty paths
+      return null;
+    }
+
+    for (i = 0; i < data.byteLength;) {
+      size  = toUnsigned(data[i]     << 24 |
+                         data[i + 1] << 16 |
+                         data[i + 2] <<  8 |
+                         data[i + 3]);
+
+      type = parseType(data.subarray(i + 4, i + 8));
+
+      end = size > 1 ? i + size : data.byteLength;
+
+      if (type === path[0]) {
+        if (path.length === 1) {
+          // this is the end of the path and we've found the box we were
+          // looking for
+          results.push(data.subarray(i + 8, end));
+        } else {
+          // recursively search for the next box along the path
+          subresults = findBox(data.subarray(i + 8, end), path.slice(1));
+          if (subresults.length) {
+            results = results.concat(subresults);
+          }
+        }
+      }
+      i = end;
+    }
+
+    // we've finished searching all of data
+    return results;
+  },
   nalParse = function(avcStream) {
@@ -845,2 +895,4 @@ var
   textify: textifyMp4,
+  parseType: parseType,
+  findBox: findBox,
   parseTraf: parse.traf,
@@ -847,0 +899,0 @@ parseTfdt: parse.tfdt,

package.json

 {
   "name": "mux.js",
-  "version": "5.3.1",
+  "version": "5.4.0",
   "description": "A collection of lightweight utilities for inspecting and manipulating video container formats.",
@@ -5,0 +5,0 @@ "repository": {

New alerts

License Policy Violation

License

This package is not allowed per your license policy. Review the package's license to ensure compliance.

Found 1 instance in 1 package

Fixed alerts

License Policy Violation

License

This package is not allowed per your license policy. Review the package's license to ensure compliance.

Found 1 instance in 1 package

Improved metrics

Total package byte prevSize

1226473

increased by0.76%

Lines of code

29280

increased by0.5%

No dependency changes