Add 'pssh' box for clear lead fragments as well

This is to workaround a Chrome limitation that CDM must be initialized
before starting the playback. CDM can only be initialized with a valid
'pssh'.

Change-Id: Ia34e90dac42abbcdf0193fe4e3c971c87debdd42

media/formats/mp4/encrypting_fragmenter.cc

@@ -51,11 +51,12 @@ Status EncryptingFragmenter::InitializeFragment() {
   if (!status.ok())
     return status;
 
-  // Enable encryption for this fragment if |clear_time_| becomes non-positive.
-  if (clear_time_ <= 0)
-    return PrepareFragmentForEncryption();
+  traf()->auxiliary_size.sample_info_sizes.clear();
+  traf()->auxiliary_offset.offsets.clear();
 
-  // Otherwise, this fragment should be in clear text.
+  const bool enable_encryption = clear_time_ <= 0;
+  if (!enable_encryption) {
+    // This fragment should be in clear text.
     // At most two sample description entries, an encrypted entry and a clear
     // entry, are generated. The 1-based clear entry index is always 2.
     const uint32 kClearSampleDescriptionIndex = 2;
@@ -63,8 +64,8 @@ Status EncryptingFragmenter::InitializeFragment() {
     traf()->header.flags |=
         TrackFragmentHeader::kSampleDescriptionIndexPresentMask;
     traf()->header.sample_description_index = kClearSampleDescriptionIndex;
-
-  return Status::OK;
+  }
+  return PrepareFragmentForEncryption(enable_encryption);
 }
 
 void EncryptingFragmenter::FinalizeFragment() {
@@ -78,10 +79,9 @@ void EncryptingFragmenter::FinalizeFragment() {
   Fragmenter::FinalizeFragment();
 }
 
-Status EncryptingFragmenter::PrepareFragmentForEncryption() {
-  traf()->auxiliary_size.sample_info_sizes.clear();
-  traf()->auxiliary_offset.offsets.clear();
-  return encryptor_ ? Status::OK : CreateEncryptor();
+Status EncryptingFragmenter::PrepareFragmentForEncryption(
+    bool enable_encryption) {
+  return (!enable_encryption || encryptor_) ? Status::OK : CreateEncryptor();
 }
 
 void EncryptingFragmenter::FinalizeFragmentForEncryption() {

media/formats/mp4/encrypting_fragmenter.h

@@ -45,7 +45,7 @@ class EncryptingFragmenter : public Fragmenter {
  protected:
   /// Prepare current fragment for encryption.
   /// @return OK on success, an error status otherwise.
-  virtual Status PrepareFragmentForEncryption();
+  virtual Status PrepareFragmentForEncryption(bool enable_encryption);
   /// Finalize current fragment for encryption.
   virtual void FinalizeFragmentForEncryption();
 

media/formats/mp4/key_rotation_fragmenter.cc

@@ -37,9 +37,9 @@ KeyRotationFragmenter::KeyRotationFragmenter(
 
 KeyRotationFragmenter::~KeyRotationFragmenter() {}
 
-Status KeyRotationFragmenter::PrepareFragmentForEncryption() {
-  traf()->auxiliary_size.sample_info_sizes.clear();
-  traf()->auxiliary_offset.offsets.clear();
+Status KeyRotationFragmenter::PrepareFragmentForEncryption(
+    bool enable_encryption) {
+  bool need_to_refresh_encryptor = !encryptor();
 
   size_t current_crypto_period_index =
       traf()->decode_time.decode_time / crypto_period_duration_;
@@ -50,17 +50,34 @@ Status KeyRotationFragmenter::PrepareFragmentForEncryption() {
     if (!status.ok())
       return status;
     set_encryption_key(encryption_key.Pass());
-
-    status = CreateEncryptor();
-    if (!status.ok())
-      return status;
     prev_crypto_period_index_ = current_crypto_period_index;
+    need_to_refresh_encryptor = true;
   }
 
-  EncryptionKey* encryption_key = EncryptingFragmenter::encryption_key();
-  DCHECK(encryption_key);
-  AesCtrEncryptor* encryptor = EncryptingFragmenter::encryptor();
-  DCHECK(encryptor);
+  // One and only one 'pssh' box is needed.
+  if (moof_->pssh.empty())
+    moof_->pssh.resize(1);
+  DCHECK(encryption_key());
+  moof_->pssh[0].raw_box = encryption_key()->pssh;
+
+  // Skip the following steps if the current fragment is not going to be
+  // encrypted. 'pssh' box needs to be included in the fragment, which is
+  // performed above, regardless of whether the fragment is encrypted. This is
+  // necessary for two reasons: 1) Requesting keys before reaching encrypted
+  // content avoids playback delay due to license requests; 2) In Chrome, CDM
+  // must be initialized before starting the playback and CDM can only be
+  // initialized with a valid 'pssh'.
+  if (!enable_encryption) {
+    DCHECK(!encryptor());
+    return Status::OK;
+  }
+
+  if (need_to_refresh_encryptor) {
+    Status status = CreateEncryptor();
+    if (!status.ok())
+      return status;
+  }
+  DCHECK(encryptor());
 
   // Key rotation happens in fragment boundary only in this implementation,
   // i.e. there is at most one key for the fragment. So there should be only
@@ -69,8 +86,9 @@ Status KeyRotationFragmenter::PrepareFragmentForEncryption() {
   traf()->sample_group_description.grouping_type = FOURCC_SEIG;
   traf()->sample_group_description.entries.resize(1);
   traf()->sample_group_description.entries[0].is_encrypted = true;
-  traf()->sample_group_description.entries[0].iv_size = encryptor->iv().size();
-  traf()->sample_group_description.entries[0].key_id = encryption_key->key_id;
+  traf()->sample_group_description.entries[0].iv_size =
+      encryptor()->iv().size();
+  traf()->sample_group_description.entries[0].key_id = encryption_key()->key_id;
 
   // Fill in SampleToGroup box information.
   traf()->sample_to_group.grouping_type = FOURCC_SEIG;
@@ -79,11 +97,6 @@ Status KeyRotationFragmenter::PrepareFragmentForEncryption() {
   traf()->sample_to_group.entries[0].group_description_index =
       SampleToGroupEntry::kTrackFragmentGroupDescriptionIndexBase + 1;
 
-  // One and only one 'pssh' box is needed.
-  if (moof_->pssh.empty())
-    moof_->pssh.resize(1);
-  moof_->pssh[0].raw_box = encryption_key->pssh;
-
   return Status::OK;
 }
 

media/formats/mp4/key_rotation_fragmenter.h

@@ -46,7 +46,7 @@ class KeyRotationFragmenter : public EncryptingFragmenter {
  protected:
   /// @name Fragmenter implementation overrides.
   /// @{
-  virtual Status PrepareFragmentForEncryption() OVERRIDE;
+  virtual Status PrepareFragmentForEncryption(bool enable_encryption) OVERRIDE;
   virtual void FinalizeFragmentForEncryption() OVERRIDE;
   /// @}