media config: expand is_encrypted to a struct.

chromecast/public/media/decoder_config.h

Index: chromecast/public/media/decoder_config.h
diff --git a/chromecast/public/media/decoder_config.h b/chromecast/public/media/decoder_config.h
index 261b3f1fa575667196ef681dedec74f7bacdb49b..9da48cc95953cca0ce57b4355680cecdd96df44b 100644
--- a/chromecast/public/media/decoder_config.h
+++ b/chromecast/public/media/decoder_config.h
@@ -93,13 +93,82 @@ enum VideoProfile {
   kVideoProfileMax = kDolbyVisionNonCompatible_BL_EL_MD,
 };
 
-// TODO(erickung): Remove constructor once CMA backend implementation does't
+// Specification of whether and how the stream is encrypted (in whole or part).
+struct EncryptionScheme {
+  // Algorithm and mode that was used to encrypt the stream.
+  enum CipherMode {
+    CIPHER_MODE_UNENCRYPTED,
+    CIPHER_MODE_AES_CTR,
+    CIPHER_MODE_AES_CBC
+  };
+
+  // CENC 3rd Edition adds pattern encryption, through two new protection
+  // schemes: 'cens' (with AES-CTR) and 'cbcs' (with AES-CBC).
+  // The pattern applies independently to each 'encrypted' part of the frame (as
+  // defined by the relevant subsample entries), and reduces further the
+  // actual encryption applied through a repeating pattern of (encrypt:skip)
+  // 16 byte blocks. For example, in a (1:9) pattern, the first block is
+  // encrypted, and the next nine are skipped. This pattern is applied
+  // repeatedly until the end of the last 16-byte block in the subsample.
+  // Any remaining bytes are left clear.
+  // If either of encrypt_blocks or skip_blocks is 0, pattern encryption is
+  // disabled.
+  struct Pattern {
+    Pattern() {}
+    Pattern(uint32_t encrypt_blocks, uint32_t skip_blocks);
+    ~Pattern() {}
+    bool IsInEffect() const;
+
+    uint32_t encrypt_blocks = 0;
+    uint32_t skip_blocks = 0;
+  };
+
+  EncryptionScheme() {}
+  explicit EncryptionScheme(CipherMode mode);
+  EncryptionScheme(CipherMode mode, const Pattern& pattern);
+  ~EncryptionScheme() {}
+  bool is_encrypted() const { return mode != CIPHER_MODE_UNENCRYPTED; }
+
+  CipherMode mode = CIPHER_MODE_UNENCRYPTED;
+  Pattern pattern;
+};
+
+inline EncryptionScheme::Pattern::Pattern(uint32_t encrypt_blocks,
+                                          uint32_t skip_blocks)
+    : encrypt_blocks(encrypt_blocks), skip_blocks(skip_blocks) {
+}
+
+inline bool EncryptionScheme::Pattern::IsInEffect() const {
+  return encrypt_blocks != 0 && skip_blocks != 0;
+}
+
+inline EncryptionScheme::EncryptionScheme(CipherMode mode)
+    : mode(mode), pattern() {
+}
+
+inline EncryptionScheme::EncryptionScheme(CipherMode mode,
+                                          const Pattern& pattern)
+    : mode(mode), pattern(pattern) {
+}
+
+inline EncryptionScheme Unencrypted() {
+  return EncryptionScheme(EncryptionScheme::CIPHER_MODE_UNENCRYPTED);
+}
+
+inline EncryptionScheme AesCtrEncryptionScheme() {
+  return EncryptionScheme(EncryptionScheme::CIPHER_MODE_AES_CTR);
+}
+
+
+// TODO(erickung): Remove constructor once CMA backend implementation doesn't
 // create a new object to reset the configuration and use IsValidConfig() to
 // determine if the configuration is still valid or not.
 struct AudioConfig {
   AudioConfig();
   ~AudioConfig();
 
+  bool is_encrypted() const { return encryption_scheme.is_encrypted(); }
+
   // Stream id.
   StreamId id;
   // Audio codec.
@@ -114,8 +183,8 @@ struct AudioConfig {
   int samples_per_second;
   // Extra data buffer for certain codec initialization.
   std::vector<uint8_t> extra_data;
-  // content is encrypted or not.
-  bool is_encrypted;
+  // Encryption scheme (if any) used for the content.
+  EncryptionScheme encryption_scheme;
 };
 
 inline AudioConfig::AudioConfig()
@@ -124,8 +193,7 @@ inline AudioConfig::AudioConfig()
       sample_format(kUnknownSampleFormat),
       bytes_per_channel(0),
       channel_number(0),
-      samples_per_second(0),
-      is_encrypted(false) {
+      samples_per_second(0) {
 }
 
 inline AudioConfig::~AudioConfig() {
@@ -138,6 +206,8 @@ struct VideoConfig {
   VideoConfig();
   ~VideoConfig();
 
+  bool is_encrypted() const { return encryption_scheme.is_encrypted(); }
+
   // Stream Id.
   StreamId id;
   // Video codec.
@@ -150,16 +220,15 @@ struct VideoConfig {
   VideoConfig* additional_config;
   // Extra data buffer for certain codec initialization.
   std::vector<uint8_t> extra_data;
-  // content is encrypted or not.
-  bool is_encrypted;
+  // Encryption scheme (if any) used for the content.
+  EncryptionScheme encryption_scheme;
 };
 
 inline VideoConfig::VideoConfig()
     : id(kPrimary),
       codec(kVideoCodecUnknown),
       profile(kVideoProfileUnknown),
-      additional_config(nullptr),
-      is_encrypted(false) {
+      additional_config(nullptr) {
 }
 
 inline VideoConfig::~VideoConfig() {