feat: parse ctts atom in mp4 inspector (#379)

Author: Nikola Hristov

lib/tools/mp4-inspector.js

@@ -425,6 +425,24 @@ var
         boxes: inspectMp4(data)
       };
     },
+    ctts: function(data) {
+      var
+        view = new DataView(data.buffer, data.byteOffset, data.byteLength),
+        result = {
+          version: view.getUint8(0),
+          flags: new Uint8Array(data.subarray(1, 4)),
+          compositionOffsets: []
+        },
+        entryCount = view.getUint32(4),
+        i;
+      for (i = 8; entryCount; i += 8, entryCount--) {
+        result.compositionOffsets.push({
+          sampleCount: view.getUint32(i),
+          sampleOffset: view[(result.version === 0 ? 'getUint32' :'getInt32')](i + 4)
+        });
+      }
+      return result;
+    },
     stco: function(data) {
       var
         view = new DataView(data.buffer, data.byteOffset, data.byteLength),

test/mp4-inspector.test.js

@@ -215,7 +215,7 @@ QUnit.test('can parse a moov', function(assert) {
   var result = QUnit.dump.parse(mp4.tools.inspect(new Uint8Array(data)));
   var expected = QUnit.dump.parse([{
     type: 'moov',
-    size: 1061,
+    size: 1109,
     boxes: [{
       type: 'mvhd',
       version: 1,
@@ -231,7 +231,7 @@ QUnit.test('can parse a moov', function(assert) {
       nextTrackId: 2
     }, {
       type: 'trak',
-      size: 475,
+      size: 499,
       boxes: [{
         type: 'tkhd',
         flags: new Uint8Array([0, 0, 0]),
@@ -263,7 +263,7 @@ QUnit.test('can parse a moov', function(assert) {
         }]
       }, {
         type: 'mdia',
-        size: 327,
+        size: 351,
         boxes: [{
           type: 'mdhd',
           version: 1,
@@ -283,7 +283,7 @@ QUnit.test('can parse a moov', function(assert) {
           size: 37
         }, {
           type: 'minf',
-          size: 238,
+          size: 262,
           boxes: [{
             type: 'dinf',
             size: 36,
@@ -301,7 +301,7 @@ QUnit.test('can parse a moov', function(assert) {
             }]
           }, {
             type: 'stbl',
-            size: 194,
+            size: 218,
             boxes: [{
               type: 'stsd',
               size: 114,
@@ -357,13 +357,21 @@ QUnit.test('can parse a moov', function(assert) {
               version: 1,
               flags: new Uint8Array([0, 0, 0]),
               chunkOffsets: [1]
+            }, {
+              type: 'ctts',
+              size: 24,
+              version: 0,
+              flags: new Uint8Array([0, 0, 0]),
+              compositionOffsets: [
+                { sampleCount: 1, sampleOffset: 1 }
+              ]
             }]
           }]
         }]
       }]
     }, {
       type: 'trak',
-      size: 458,
+      size: 482,
       boxes: [{
         type: 'tkhd',
         flags: new Uint8Array([0, 0, 0]),
@@ -395,7 +403,7 @@ QUnit.test('can parse a moov', function(assert) {
         }]
       }, {
         type: 'mdia',
-        size: 302,
+        size: 326,
         boxes: [{
           type: 'mdhd',
           version: 1,
@@ -415,7 +423,7 @@ QUnit.test('can parse a moov', function(assert) {
           size: 37
         }, {
           type: 'minf',
-          size: 213,
+          size: 237,
           boxes: [{
             type: 'dinf',
             size: 36,
@@ -433,7 +441,7 @@ QUnit.test('can parse a moov', function(assert) {
             }]
           }, {
             type: 'stbl',
-            size: 169,
+            size: 193,
             boxes: [{
               type: 'stsd',
               size: 89,
@@ -492,6 +500,14 @@ QUnit.test('can parse a moov', function(assert) {
                 sampleDescriptionIndex: 1
               }],
               size: 28
+            }, {
+              type: 'ctts',
+              size: 24,
+              version: 1,
+              flags: new Uint8Array([0, 0, 0]),
+              compositionOffsets: [
+                { sampleCount: 1, sampleOffset: -1 }
+              ]
             }, {
               type: 'stco',
               size: 20,

test/utils/mp4-helpers.js

@@ -194,7 +194,13 @@ module.exports.sampleMoov =
                           0x01, // version 1
                           0x00, 0x00, 0x00, // flags
                           0x00, 0x00, 0x00, 0x01, // entry_count
-                          0x00, 0x00, 0x00, 0x01))))), // chunk_offset
+                          0x00, 0x00, 0x00, 0x01), // chunk_offset
+                      box('ctts',
+                          0x00, // version 0
+                          0x00, 0x00, 0x00, // flags
+                          0x00, 0x00, 0x00, 0x01, // entry_count
+                          0x00, 0x00, 0x00, 0x01, // sample_count
+                          0x00, 0x00, 0x00, 0x01))))), // sample_offset
       box('trak',
           box('tkhd',
               0x01, // version 1
@@ -291,6 +297,12 @@ module.exports.sampleMoov =
                           0x00, 0x00, 0x00, 0x02, // first_chunk
                           0x00, 0x00, 0x00, 0x03, // samples_per_chunk
                           0x00, 0x00, 0x00, 0x01), // sample_description_index
+                      box('ctts',
+                          0x01, // version 1
+                          0x00, 0x00, 0x00, // flags
+                          0x00, 0x00, 0x00, 0x01, // entry_count
+                          0x00, 0x00, 0x00, 0x01, // sample_count
+                          0xff, 0xff, 0xff, 0xff), // sample_offset
                       box('stco',
                           0x01, // version 1
                           0x00, 0x00, 0x00, // flags