Merge pull request #251 from videojs/hlse-perf

Optimize decryption

@@ -38,7 +38,18 @@
 (function(window, videojs, unpad) {
 (function(window, videojs, unpad) {
 'use strict';
 'use strict';
 
 
-var AES, decrypt;
+var AES, AsyncStream, Decrypter, decrypt, ntoh;
+
+/**
+ * Convert network-order (big-endian) bytes into their little-endian
+ * representation.
+ */
+ntoh = function(word) {
+  return (word << 24) |
+    ((word & 0xff00) << 8) |
+    ((word & 0xff0000) >> 8) |
+    (word >>> 24);
+};
 
 
 /**
 /**
  * Schedule out an AES key for both encryption and decryption. This
  * Schedule out an AES key for both encryption and decryption. This
@@ -49,38 +60,38 @@ var AES, decrypt;
  */
  */
 AES = function (key) {
 AES = function (key) {
   this._precompute();
   this._precompute();
-  
+
   var i, j, tmp,
   var i, j, tmp,
     encKey, decKey,
     encKey, decKey,
     sbox = this._tables[0][4], decTable = this._tables[1],
     sbox = this._tables[0][4], decTable = this._tables[1],
     keyLen = key.length, rcon = 1;
     keyLen = key.length, rcon = 1;
-  
+
   if (keyLen !== 4 && keyLen !== 6 && keyLen !== 8) {
   if (keyLen !== 4 && keyLen !== 6 && keyLen !== 8) {
     throw new Error("Invalid aes key size");
     throw new Error("Invalid aes key size");
   }
   }
-  
+
   encKey = key.slice(0);
   encKey = key.slice(0);
   decKey = [];
   decKey = [];
   this._key = [encKey, decKey];
   this._key = [encKey, decKey];
-  
+
   // schedule encryption keys
   // schedule encryption keys
   for (i = keyLen; i < 4 * keyLen + 28; i++) {
   for (i = keyLen; i < 4 * keyLen + 28; i++) {
     tmp = encKey[i-1];
     tmp = encKey[i-1];
-    
+
     // apply sbox
     // apply sbox
     if (i%keyLen === 0 || (keyLen === 8 && i%keyLen === 4)) {
     if (i%keyLen === 0 || (keyLen === 8 && i%keyLen === 4)) {
       tmp = sbox[tmp>>>24]<<24 ^ sbox[tmp>>16&255]<<16 ^ sbox[tmp>>8&255]<<8 ^ sbox[tmp&255];
       tmp = sbox[tmp>>>24]<<24 ^ sbox[tmp>>16&255]<<16 ^ sbox[tmp>>8&255]<<8 ^ sbox[tmp&255];
-      
+
       // shift rows and add rcon
       // shift rows and add rcon
       if (i%keyLen === 0) {
       if (i%keyLen === 0) {
         tmp = tmp<<8 ^ tmp>>>24 ^ rcon<<24;
         tmp = tmp<<8 ^ tmp>>>24 ^ rcon<<24;
         rcon = rcon<<1 ^ (rcon>>7)*283;
         rcon = rcon<<1 ^ (rcon>>7)*283;
       }
       }
     }
     }
-    
+
     encKey[i] = encKey[i-keyLen] ^ tmp;
     encKey[i] = encKey[i-keyLen] ^ tmp;
   }
   }
-  
+
   // schedule decryption keys
   // schedule decryption keys
   for (j = 0; i; j++, i--) {
   for (j = 0; i; j++, i--) {
     tmp = encKey[j&3 ? i : i - 4];
     tmp = encKey[j&3 ? i : i - 4];
@@ -124,126 +135,231 @@ AES.prototype = {
    for (i = 0; i < 256; i++) {
    for (i = 0; i < 256; i++) {
      th[( d[i] = i<<1 ^ (i>>7)*283 )^i]=i;
      th[( d[i] = i<<1 ^ (i>>7)*283 )^i]=i;
    }
    }
-   
+
    for (x = xInv = 0; !sbox[x]; x ^= x2 || 1, xInv = th[xInv] || 1) {
    for (x = xInv = 0; !sbox[x]; x ^= x2 || 1, xInv = th[xInv] || 1) {
      // Compute sbox
      // Compute sbox
      s = xInv ^ xInv<<1 ^ xInv<<2 ^ xInv<<3 ^ xInv<<4;
      s = xInv ^ xInv<<1 ^ xInv<<2 ^ xInv<<3 ^ xInv<<4;
      s = s>>8 ^ s&255 ^ 99;
      s = s>>8 ^ s&255 ^ 99;
      sbox[x] = s;
      sbox[x] = s;
      sboxInv[s] = x;
      sboxInv[s] = x;
-     
+
      // Compute MixColumns
      // Compute MixColumns
      x8 = d[x4 = d[x2 = d[x]]];
      x8 = d[x4 = d[x2 = d[x]]];
      tDec = x8*0x1010101 ^ x4*0x10001 ^ x2*0x101 ^ x*0x1010100;
      tDec = x8*0x1010101 ^ x4*0x10001 ^ x2*0x101 ^ x*0x1010100;
      tEnc = d[s]*0x101 ^ s*0x1010100;
      tEnc = d[s]*0x101 ^ s*0x1010100;
-     
+
      for (i = 0; i < 4; i++) {
      for (i = 0; i < 4; i++) {
        encTable[i][x] = tEnc = tEnc<<24 ^ tEnc>>>8;
        encTable[i][x] = tEnc = tEnc<<24 ^ tEnc>>>8;
        decTable[i][s] = tDec = tDec<<24 ^ tDec>>>8;
        decTable[i][s] = tDec = tDec<<24 ^ tDec>>>8;
      }
      }
    }
    }
-   
+
    // Compactify. Considerable speedup on Firefox.
    // Compactify. Considerable speedup on Firefox.
    for (i = 0; i < 5; i++) {
    for (i = 0; i < 5; i++) {
      encTable[i] = encTable[i].slice(0);
      encTable[i] = encTable[i].slice(0);
      decTable[i] = decTable[i].slice(0);
      decTable[i] = decTable[i].slice(0);
    }
    }
   },
   },
-  
+
   /**
   /**
-   * Decrypt an array of 4 big-endian words.
-   * @param {Array} data The ciphertext.
+   * Decrypt 16 bytes, specified as four 32-bit words.
+   * @param encrypted0 {number} the first word to decrypt
+   * @param encrypted1 {number} the second word to decrypt
+   * @param encrypted2 {number} the third word to decrypt
+   * @param encrypted3 {number} the fourth word to decrypt
+   * @param out {Int32Array} the array to write the decrypted words
+   * into
+   * @param offset {number} the offset into the output array to start
+   * writing results
    * @return {Array} The plaintext.
    * @return {Array} The plaintext.
    */
    */
-  decrypt:function (input) {
-    if (input.length !== 4) {
-      throw new Error("Invalid aes block size");
-    }
-    
+  decrypt:function (encrypted0, encrypted1, encrypted2, encrypted3, out, offset) {
     var key = this._key[1],
     var key = this._key[1],
         // state variables a,b,c,d are loaded with pre-whitened data
         // state variables a,b,c,d are loaded with pre-whitened data
-        a = input[0]           ^ key[0],
-        b = input[3] ^ key[1],
-        c = input[2]           ^ key[2],
-        d = input[1] ^ key[3],
+        a = encrypted0 ^ key[0],
+        b = encrypted3 ^ key[1],
+        c = encrypted2 ^ key[2],
+        d = encrypted1 ^ key[3],
         a2, b2, c2,
         a2, b2, c2,
-        
-        nInnerRounds = key.length/4 - 2,
+
+        nInnerRounds = key.length / 4 - 2, // key.length === 2 ?
         i,
         i,
         kIndex = 4,
         kIndex = 4,
-        out = [0,0,0,0],
         table = this._tables[1],
         table = this._tables[1],
-        
+
         // load up the tables
         // load up the tables
-        t0    = table[0],
-        t1    = table[1],
-        t2    = table[2],
-        t3    = table[3],
+        table0    = table[0],
+        table1    = table[1],
+        table2    = table[2],
+        table3    = table[3],
         sbox  = table[4];
         sbox  = table[4];
- 
+
     // Inner rounds. Cribbed from OpenSSL.
     // Inner rounds. Cribbed from OpenSSL.
     for (i = 0; i < nInnerRounds; i++) {
     for (i = 0; i < nInnerRounds; i++) {
-      a2 = t0[a>>>24] ^ t1[b>>16 & 255] ^ t2[c>>8 & 255] ^ t3[d & 255] ^ key[kIndex];
-      b2 = t0[b>>>24] ^ t1[c>>16 & 255] ^ t2[d>>8 & 255] ^ t3[a & 255] ^ key[kIndex + 1];
-      c2 = t0[c>>>24] ^ t1[d>>16 & 255] ^ t2[a>>8 & 255] ^ t3[b & 255] ^ key[kIndex + 2];
-      d  = t0[d>>>24] ^ t1[a>>16 & 255] ^ t2[b>>8 & 255] ^ t3[c & 255] ^ key[kIndex + 3];
+      a2 = table0[a>>>24] ^ table1[b>>16 & 255] ^ table2[c>>8 & 255] ^ table3[d & 255] ^ key[kIndex];
+      b2 = table0[b>>>24] ^ table1[c>>16 & 255] ^ table2[d>>8 & 255] ^ table3[a & 255] ^ key[kIndex + 1];
+      c2 = table0[c>>>24] ^ table1[d>>16 & 255] ^ table2[a>>8 & 255] ^ table3[b & 255] ^ key[kIndex + 2];
+      d  = table0[d>>>24] ^ table1[a>>16 & 255] ^ table2[b>>8 & 255] ^ table3[c & 255] ^ key[kIndex + 3];
       kIndex += 4;
       kIndex += 4;
       a=a2; b=b2; c=c2;
       a=a2; b=b2; c=c2;
     }
     }
-        
+
     // Last round.
     // Last round.
     for (i = 0; i < 4; i++) {
     for (i = 0; i < 4; i++) {
-      out[3 & -i] =
-        sbox[a>>>24      ]<<24 ^ 
+      out[(3 & -i) + offset] =
+        sbox[a>>>24      ]<<24 ^
         sbox[b>>16  & 255]<<16 ^
         sbox[b>>16  & 255]<<16 ^
         sbox[c>>8   & 255]<<8  ^
         sbox[c>>8   & 255]<<8  ^
         sbox[d      & 255]     ^
         sbox[d      & 255]     ^
         key[kIndex++];
         key[kIndex++];
       a2=a; a=b; b=c; c=d; d=a2;
       a2=a; a=b; b=c; c=d; d=a2;
     }
     }
-    
-    return out;
   }
   }
 };
 };
 
 
+/**
+ * Decrypt bytes using AES-128 with CBC and PKCS#7 padding.
+ * @param encrypted {Uint8Array} the encrypted bytes
+ * @param key {Uint32Array} the bytes of the decryption key
+ * @param initVector {Uint32Array} the initialization vector (IV) to
+ * use for the first round of CBC.
+ * @return {Uint8Array} the decrypted bytes
+ *
+ * @see http://en.wikipedia.org/wiki/Advanced_Encryption_Standard
+ * @see http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Cipher_Block_Chaining_.28CBC.29
+ * @see https://tools.ietf.org/html/rfc2315
+ */
 decrypt = function(encrypted, key, initVector) {
 decrypt = function(encrypted, key, initVector) {
   var
   var
-    encryptedView = new DataView(encrypted.buffer),
-    platformEndian = new Uint32Array(encrypted.byteLength / 4),
+    // word-level access to the encrypted bytes
+    encrypted32 = new Int32Array(encrypted.buffer, encrypted.byteOffset, encrypted.byteLength >> 2),
+
     decipher = new AES(Array.prototype.slice.call(key)),
     decipher = new AES(Array.prototype.slice.call(key)),
+
+    // byte and word-level access for the decrypted output
     decrypted = new Uint8Array(encrypted.byteLength),
     decrypted = new Uint8Array(encrypted.byteLength),
-    decryptedView = new DataView(decrypted.buffer),
-    decryptedBlock,
-    word,
-    byte;
-
-  // convert big-endian input to platform byte order for decryption
-  for (byte = 0; byte < encrypted.byteLength; byte += 4) {
-    platformEndian[byte >>> 2] = encryptedView.getUint32(byte);
-  }
+    decrypted32 = new Int32Array(decrypted.buffer),
+
+    // temporary variables for working with the IV, encrypted, and
+    // decrypted data
+    init0, init1, init2, init3,
+    encrypted0, encrypted1, encrypted2, encrypted3,
+
+    // iteration variable
+    wordIx;
+
+  // pull out the words of the IV to ensure we don't modify the
+  // passed-in reference and easier access
+  init0 = initVector[0];
+  init1 = initVector[1];
+  init2 = initVector[2];
+  init3 = initVector[3];
+
   // decrypt four word sequences, applying cipher-block chaining (CBC)
   // decrypt four word sequences, applying cipher-block chaining (CBC)
   // to each decrypted block
   // to each decrypted block
-  for (word = 0; word < platformEndian.length; word += 4) {
+  for (wordIx = 0; wordIx < encrypted32.length; wordIx += 4) {
+    // convert big-endian (network order) words into little-endian
+    // (javascript order)
+    encrypted0 = ntoh(encrypted32[wordIx]);
+    encrypted1 = ntoh(encrypted32[wordIx + 1]);
+    encrypted2 = ntoh(encrypted32[wordIx + 2]);
+    encrypted3 = ntoh(encrypted32[wordIx + 3]);
+
     // decrypt the block
     // decrypt the block
-    decryptedBlock = decipher.decrypt(platformEndian.subarray(word, word + 4));
+    decipher.decrypt(encrypted0,
+                     encrypted1,
+                     encrypted2,
+                     encrypted3,
+                     decrypted32,
+                     wordIx);
 
 
     // XOR with the IV, and restore network byte-order to obtain the
     // XOR with the IV, and restore network byte-order to obtain the
     // plaintext
     // plaintext
-    byte = word << 2;
-    decryptedView.setUint32(byte, decryptedBlock[0] ^ initVector[0]);
-    decryptedView.setUint32(byte + 4, decryptedBlock[1] ^ initVector[1]);
-    decryptedView.setUint32(byte + 8, decryptedBlock[2] ^ initVector[2]);
-    decryptedView.setUint32(byte + 12, decryptedBlock[3] ^ initVector[3]);
+    decrypted32[wordIx]     = ntoh(decrypted32[wordIx] ^ init0);
+    decrypted32[wordIx + 1] = ntoh(decrypted32[wordIx + 1] ^ init1);
+    decrypted32[wordIx + 2] = ntoh(decrypted32[wordIx + 2] ^ init2);
+    decrypted32[wordIx + 3] = ntoh(decrypted32[wordIx + 3] ^ init3);
 
 
     // setup the IV for the next round
     // setup the IV for the next round
-    initVector = platformEndian.subarray(word, word + 4);
+    init0 = encrypted0;
+    init1 = encrypted1;
+    init2 = encrypted2;
+    init3 = encrypted3;
   }
   }
 
 
-  // remove any padding
-  return unpad(decrypted);
+  return decrypted;
+};
+
+AsyncStream = function() {
+  this.jobs = [];
+  this.delay = 1;
+  this.timeout_ = null;
+};
+AsyncStream.prototype = new videojs.Hls.Stream();
+AsyncStream.prototype.processJob_ = function() {
+  this.jobs.shift()();
+  if (this.jobs.length) {
+    this.timeout_ = setTimeout(videojs.bind(this, this.processJob_),
+                               this.delay);
+  } else {
+    this.timeout_ = null;
+  }
+};
+AsyncStream.prototype.push = function(job) {
+  this.jobs.push(job);
+  if (!this.timeout_) {
+    this.timeout_ = setTimeout(videojs.bind(this, this.processJob_),
+                               this.delay);
+  }
+};
+
+Decrypter = function(encrypted, key, initVector, done) {
+  var
+    step = Decrypter.STEP,
+    encrypted32 = new Int32Array(encrypted.buffer),
+    decrypted = new Uint8Array(encrypted.byteLength),
+    i = 0;
+  this.asyncStream_ = new AsyncStream();
+
+  // split up the encryption job and do the individual chunks asynchronously
+  this.asyncStream_.push(this.decryptChunk_(encrypted32.subarray(i, i + step),
+                                            key,
+                                            initVector,
+                                            decrypted,
+                                            i));
+  for (i = step; i < encrypted32.length; i += step) {
+    initVector = new Uint32Array([
+      ntoh(encrypted32[i - 4]),
+      ntoh(encrypted32[i - 3]),
+      ntoh(encrypted32[i - 2]),
+      ntoh(encrypted32[i - 1])
+    ]);
+    this.asyncStream_.push(this.decryptChunk_(encrypted32.subarray(i, i + step),
+                                              key,
+                                              initVector,
+                                              decrypted));
+  }
+  // invoke the done() callback when everything is finished
+  this.asyncStream_.push(function() {
+    // remove pkcs#7 padding from the decrypted bytes
+    done(null, unpad(decrypted));
+  });
+};
+Decrypter.prototype = new videojs.Hls.Stream();
+Decrypter.prototype.decryptChunk_ = function(encrypted, key, initVector, decrypted) {
+  return function() {
+    var bytes = decrypt(encrypted,
+                        key,
+                        initVector);
+    decrypted.set(bytes, encrypted.byteOffset);
+  };
 };
 };
+// the maximum number of bytes to process at one time
+Decrypter.STEP = 4 * 8000;
 
 
 // exports
 // exports
 videojs.Hls.decrypt = decrypt;
 videojs.Hls.decrypt = decrypt;
+videojs.Hls.Decrypter = Decrypter;
+videojs.Hls.AsyncStream = AsyncStream;
 
 
 })(window, window.videojs, window.pkcs7.unpad);
 })(window, window.videojs, window.pkcs7.unpad);

@@ -637,6 +637,8 @@ videojs.Hls.prototype.loadSegment = function(segmentUri, offset) {
     responseType: 'arraybuffer',
     responseType: 'arraybuffer',
     withCredentials: settings.withCredentials
     withCredentials: settings.withCredentials
   }, function(error, url) {
   }, function(error, url) {
+    var segmentInfo;
+
     // the segment request is no longer outstanding
     // the segment request is no longer outstanding
     tech.segmentXhr_ = null;
     tech.segmentXhr_ = null;
 
 
@@ -669,12 +671,26 @@ videojs.Hls.prototype.loadSegment = function(segmentUri, offset) {
     // if the segment is the start of a timestamp discontinuity,
     // if the segment is the start of a timestamp discontinuity,
     // we have to wait until the sourcebuffer is empty before
     // we have to wait until the sourcebuffer is empty before
     // aborting the source buffer processing
     // aborting the source buffer processing
-    tech.segmentBuffer_.push({
+    segmentInfo = {
+      // the segment's mediaIndex at the time it was received
       mediaIndex: tech.mediaIndex,
       mediaIndex: tech.mediaIndex,
+      // the segment's playlist
       playlist: tech.playlists.media(),
       playlist: tech.playlists.media(),
+      // optionally, a time offset to seek to within the segment
       offset: offset,
       offset: offset,
-      bytes: new Uint8Array(this.response)
-    });
+      // unencrypted bytes of the segment
+      bytes: null,
+      // when a key is defined for this segment, the encrypted bytes
+      encryptedBytes: null,
+      // optionally, the decrypter that is unencrypting the segment
+      decrypter: null
+    };
+    if (segmentInfo.playlist.segments[segmentInfo.mediaIndex].key) {
+      segmentInfo.encryptedBytes = new Uint8Array(this.response);
+    } else {
+      segmentInfo.bytes = new Uint8Array(this.response);
+    }
+    tech.segmentBuffer_.push(segmentInfo);
     player.trigger('progress');
     player.trigger('progress');
     tech.drainBuffer();
     tech.drainBuffer();
 
 
@@ -689,12 +705,15 @@ videojs.Hls.prototype.loadSegment = function(segmentUri, offset) {
 videojs.Hls.prototype.drainBuffer = function(event) {
 videojs.Hls.prototype.drainBuffer = function(event) {
   var
   var
     i = 0,
     i = 0,
+    segmentInfo,
     mediaIndex,
     mediaIndex,
     playlist,
     playlist,
     offset,
     offset,
     tags,
     tags,
     bytes,
     bytes,
     segment,
     segment,
+    decrypter,
+    segIv,
 
 
     ptsTime,
     ptsTime,
     segmentOffset,
     segmentOffset,
@@ -704,28 +723,45 @@ videojs.Hls.prototype.drainBuffer = function(event) {
     return;
     return;
   }
   }
 
 
-  mediaIndex = segmentBuffer[0].mediaIndex;
-  playlist = segmentBuffer[0].playlist;
-  offset = segmentBuffer[0].offset;
-  bytes = segmentBuffer[0].bytes;
+  segmentInfo = segmentBuffer[0];
+
+  mediaIndex = segmentInfo.mediaIndex;
+  playlist = segmentInfo.playlist;
+  offset = segmentInfo.offset;
+  bytes = segmentInfo.bytes;
   segment = playlist.segments[mediaIndex];
   segment = playlist.segments[mediaIndex];
 
 
-  if (segment.key) {
+  if (segment.key && !bytes) {
+
     // this is an encrypted segment
     // this is an encrypted segment
     // if the key download failed, we want to skip this segment
     // if the key download failed, we want to skip this segment
     // but if the key hasn't downloaded yet, we want to try again later
     // but if the key hasn't downloaded yet, we want to try again later
     if (keyFailed(segment.key)) {
     if (keyFailed(segment.key)) {
       return segmentBuffer.shift();
       return segmentBuffer.shift();
     } else if (!segment.key.bytes) {
     } else if (!segment.key.bytes) {
+
       // trigger a key request if one is not already in-flight
       // trigger a key request if one is not already in-flight
       return this.fetchKeys_();
       return this.fetchKeys_();
+
+    } else if (segmentInfo.decrypter) {
+
+      // decryption is in progress, try again later
+      return;
+
     } else {
     } else {
       // if the media sequence is greater than 2^32, the IV will be incorrect
       // if the media sequence is greater than 2^32, the IV will be incorrect
       // assuming 10s segments, that would be about 1300 years
       // assuming 10s segments, that would be about 1300 years
-      var segIv = segment.key.iv || new Uint32Array([0, 0, 0, mediaIndex + playlist.mediaSequence]);
-      bytes = videojs.Hls.decrypt(bytes,
-                                  segment.key.bytes,
-                                  segIv);
+      segIv = segment.key.iv || new Uint32Array([0, 0, 0, mediaIndex + playlist.mediaSequence]);
+
+      // create a decrypter to incrementally decrypt the segment
+      decrypter = new videojs.Hls.Decrypter(segmentInfo.encryptedBytes,
+                                            segment.key.bytes,
+                                            segIv,
+                                            function(err, bytes) {
+                                              segmentInfo.bytes = bytes;
+                                            });
+      segmentInfo.decrypter = decrypter;
+      return;
     }
     }
   }
   }
 
 

-(function(window, videojs, undefined) {
+(function(window, videojs, unpad, undefined) {
   'use strict';
   'use strict';
   /*
   /*
     ======== A Handy Little QUnit Reference ========
     ======== A Handy Little QUnit Reference ========
@@ -46,7 +46,7 @@ test('decrypts a single AES-128 with PKCS7 block', function() {
       0x82, 0xa8, 0xf0, 0x67]);
       0x82, 0xa8, 0xf0, 0x67]);
 
 
   deepEqual('howdy folks',
   deepEqual('howdy folks',
-            stringFromBytes(videojs.Hls.decrypt(encrypted, key, initVector)),
+            stringFromBytes(unpad(videojs.Hls.decrypt(encrypted, key, initVector))),
             'decrypted with a byte array key');
             'decrypted with a byte array key');
 });
 });
 
 
@@ -68,8 +68,100 @@ test('decrypts multiple AES-128 blocks with CBC', function() {
     ]);
     ]);
 
 
   deepEqual('0123456789abcdef01234',
   deepEqual('0123456789abcdef01234',
-            stringFromBytes(videojs.Hls.decrypt(encrypted, key, initVector)),
+            stringFromBytes(unpad(videojs.Hls.decrypt(encrypted, key, initVector))),
             'decrypted multiple blocks');
             'decrypted multiple blocks');
 });
 });
 
 
-})(window, window.videojs);
+var clock;
+
+module('Incremental Processing', {
+  setup: function() {
+    clock = sinon.useFakeTimers();
+  },
+  teardown: function() {
+    clock.restore();
+  }
+});
+
+test('executes a callback after a timeout', function() {
+  var asyncStream = new videojs.Hls.AsyncStream(),
+      calls = '';
+  asyncStream.push(function() {
+    calls += 'a';
+  });
+
+  clock.tick(asyncStream.delay);
+  equal(calls, 'a', 'invoked the callback once');
+  clock.tick(asyncStream.delay);
+  equal(calls, 'a', 'only invoked the callback once');
+});
+
+test('executes callback in series', function() {
+  var asyncStream = new videojs.Hls.AsyncStream(),
+      calls = '';
+  asyncStream.push(function() {
+    calls += 'a';
+  });
+  asyncStream.push(function() {
+    calls += 'b';
+  });
+
+  clock.tick(asyncStream.delay);
+  equal(calls, 'a', 'invoked the first callback');
+  clock.tick(asyncStream.delay);
+  equal(calls, 'ab', 'invoked the second');
+});
+
+var decrypter;
+
+module('Incremental Decryption', {
+  setup: function() {
+    clock = sinon.useFakeTimers();
+  },
+  teardown: function() {
+    clock.restore();
+  }
+});
+
+test('asynchronously decrypts a 4-word block', function() {
+  var
+    key =  new Uint32Array([0, 0, 0, 0]),
+    initVector = key,
+    // the string "howdy folks" encrypted
+    encrypted = new Uint8Array([
+      0xce, 0x90, 0x97, 0xd0,
+      0x08, 0x46, 0x4d, 0x18,
+      0x4f, 0xae, 0x01, 0x1c,
+      0x82, 0xa8, 0xf0, 0x67]),
+    decrypted;
+
+  decrypter = new videojs.Hls.Decrypter(encrypted, key, initVector, function(error, result) {
+    decrypted = result;
+  });
+  ok(!decrypted, 'asynchronously decrypts');
+
+  clock.tick(decrypter.asyncStream_.delay * 2);
+
+  ok(decrypted, 'completed decryption');
+  deepEqual('howdy folks',
+            stringFromBytes(decrypted),
+            'decrypts and unpads the result');
+});
+
+test('breaks up input greater than the step value', function() {
+  var encrypted = new Int32Array(videojs.Hls.Decrypter.STEP + 4),
+      done = false,
+      decrypter = new videojs.Hls.Decrypter(encrypted,
+                                            new Uint32Array(4),
+                                            new Uint32Array(4),
+                                            function() {
+                                              done = true;
+                                            });
+  clock.tick(decrypter.asyncStream_.delay * 2);
+  ok(!done, 'not finished after two ticks');
+
+  clock.tick(decrypter.asyncStream_.delay);
+  ok(done, 'finished after the last chunk is decrypted');
+});
+
+})(window, window.videojs, window.pkcs7.unpad);

@@ -152,10 +152,8 @@ module('HLS', {
 
 
     oldNativeHlsSupport = videojs.Hls.supportsNativeHls;
     oldNativeHlsSupport = videojs.Hls.supportsNativeHls;
 
 
-    oldDecrypt = videojs.Hls.decrypt;
-    videojs.Hls.decrypt = function() {
-      return new Uint8Array([0]);
-    };
+    oldDecrypt = videojs.Hls.Decrypter;
+    videojs.Hls.Decrypter = function() {};
 
 
     // fake XHRs
     // fake XHRs
     xhr = sinon.useFakeXMLHttpRequest();
     xhr = sinon.useFakeXMLHttpRequest();
@@ -173,7 +171,7 @@ module('HLS', {
     videojs.MediaSource.open = oldMediaSourceOpen;
     videojs.MediaSource.open = oldMediaSourceOpen;
     videojs.Hls.SegmentParser = oldSegmentParser;
     videojs.Hls.SegmentParser = oldSegmentParser;
     videojs.Hls.supportsNativeHls = oldNativeHlsSupport;
     videojs.Hls.supportsNativeHls = oldNativeHlsSupport;
-    videojs.Hls.decrypt = oldDecrypt;
+    videojs.Hls.Decrypter = oldDecrypt;
     videojs.SourceBuffer = oldSourceBuffer;
     videojs.SourceBuffer = oldSourceBuffer;
     window.setTimeout = oldSetTimeout;
     window.setTimeout = oldSetTimeout;
     window.clearTimeout = oldClearTimeout;
     window.clearTimeout = oldClearTimeout;
@@ -1904,6 +1902,10 @@ test('a new key XHR is created when a the segment is received', function() {
                            '#EXT-X-ENDLIST\n');
                            '#EXT-X-ENDLIST\n');
   standardXHRResponse(requests.shift()); // segment 1
   standardXHRResponse(requests.shift()); // segment 1
   standardXHRResponse(requests.shift()); // key 1
   standardXHRResponse(requests.shift()); // key 1
+  // "finish" decrypting segment 1
+  player.hls.segmentBuffer_[0].bytes = new Uint8Array(16);
+  player.hls.checkBuffer_();
+
   standardXHRResponse(requests.shift()); // segment 2
   standardXHRResponse(requests.shift()); // segment 2
 
 
   strictEqual(requests.length, 1, 'a key XHR is created');
   strictEqual(requests.length, 1, 'a key XHR is created');
@@ -2009,6 +2011,9 @@ test('skip segments if key requests fail more than once', function() {
   // key for second segment
   // key for second segment
   requests[0].response = new Uint32Array([0,0,0,0]).buffer;
   requests[0].response = new Uint32Array([0,0,0,0]).buffer;
   requests.shift().respond(200, null, '');
   requests.shift().respond(200, null, '');
+  // "finish" decryption
+  player.hls.segmentBuffer_[0].bytes = new Uint8Array(16);
+  player.hls.checkBuffer_();
 
 
   equal(bytes.length, 2, 'bytes from the second ts segment should be added');
   equal(bytes.length, 2, 'bytes from the second ts segment should be added');
   equal(bytes[1], 1, 'the bytes from the second segment are added and not the first');
   equal(bytes[1], 1, 'the bytes from the second segment are added and not the first');
@@ -2033,9 +2038,8 @@ test('the key is supplied to the decrypter in the correct format', function() {
                          'http://media.example.com/fileSequence52-B.ts\n');
                          'http://media.example.com/fileSequence52-B.ts\n');
 
 
 
 
-  videojs.Hls.decrypt = function(bytes, key) {
+  videojs.Hls.Decrypter = function(encrypted, key) {
     keys.push(key);
     keys.push(key);
-    return new Uint8Array([0]);
   };
   };
 
 
   standardXHRResponse(requests.shift()); // segment
   standardXHRResponse(requests.shift()); // segment
@@ -2043,7 +2047,7 @@ test('the key is supplied to the decrypter in the correct format', function() {
   requests[0].respond(200, null, '');
   requests[0].respond(200, null, '');
   requests.shift(); // key
   requests.shift(); // key
 
 
-  equal(keys.length, 1, 'only one call to decrypt was made');
+  equal(keys.length, 1, 'only one Decrypter was constructed');
   deepEqual(keys[0],
   deepEqual(keys[0],
             new Uint32Array([0, 0x01000000, 0x02000000, 0x03000000]),
             new Uint32Array([0, 0x01000000, 0x02000000, 0x03000000]),
             'passed the specified segment key');
             'passed the specified segment key');
@@ -2068,9 +2072,8 @@ test('supplies the media sequence of current segment as the IV by default, if no
                          'http://media.example.com/fileSequence52-B.ts\n');
                          'http://media.example.com/fileSequence52-B.ts\n');
 
 
 
 
-  videojs.Hls.decrypt = function(bytes, key, iv) {
+  videojs.Hls.Decrypter = function(encrypted, key, iv) {
     ivs.push(iv);
     ivs.push(iv);
-    return new Uint8Array([0]);
   };
   };
 
 
   requests[0].response = new Uint32Array([0,0,0,0]).buffer;
   requests[0].response = new Uint32Array([0,0,0,0]).buffer;
@@ -2078,7 +2081,7 @@ test('supplies the media sequence of current segment as the IV by default, if no
   requests.shift();
   requests.shift();
   standardXHRResponse(requests.pop());
   standardXHRResponse(requests.pop());
 
 
-  equal(ivs.length, 1, 'only one call to decrypt was made');
+  equal(ivs.length, 1, 'only one Decrypter was constructed');
   deepEqual(ivs[0],
   deepEqual(ivs[0],
         new Uint32Array([0, 0, 0, 5]),
         new Uint32Array([0, 0, 0, 5]),
         'the IV for the segment is the media sequence');
         'the IV for the segment is the media sequence');