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..fb60fcd458a729c529677d263804f1be610fa4fc 100644
--- a/chromecast/public/media/decoder_config.h
+++ b/chromecast/public/media/decoder_config.h
@@ -93,13 +93,94 @@ 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 {

[xhwang, 2016/03/03 22:33:00]

Is there any reason you need to duplication this in chromecast code? Also, why
don't you keep it exactly the same as the one in media/base?

[halliwell, 2016/03/03 22:56:44]

Yep, we ship just this directory (chromecast/public) as headers for Cast
hardware vendors to include and build against, so they don't need a full
Chromium checkout.

I'm not sure why it's not the same as the other version though.

[dougsteed, 2016/03/04 19:07:29]

Not sure what you mean by "not the same". As far as I know it is the same except
for systemic changes: this file uses structs while media/base uses classes, etc.

[xhwang, 2016/03/04 20:00:48]

Yeah, I was talking about struct/class and unencrypted/Unencrypted.

[dougsteed, 2016/03/07 17:49:13]

I eliminated the unencrypted/Unencrypted distinction. 

+  // Algorithm and mode that was used to encrypt the stream.
+  enum CipherMode {
+    kCipherModeUnencrypted,
+    kCipherModeAesCtr,
+    kCipherModeAesCbc
+  };
+
+  // CENC 3d Edition adds pattern encryption, through two new

[ddorwin, 2016/03/03 18:38:04]

3rd

[dougsteed, 2016/03/04 19:07:29]

aargh. Done.

+  // protection schemes 'cens' (with AES-CTR) and 'cbcs' (with AES-CBC).
+  // The pattern applies only to the '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 or both of encrypt_blocks or skip_blocks is 0, pattern
+  // encryption is disabled.
+  struct PatternSpec {
+    PatternSpec();
+    PatternSpec(uint32_t encrypt_blocks, uint32_t skip_blocks);
+    ~PatternSpec();
+    bool IsInEffect() const;
+
+    uint32_t encrypt_blocks;
+    uint32_t skip_blocks;
+  };
+
+  EncryptionScheme();
+  explicit EncryptionScheme(CipherMode mode);
+  EncryptionScheme(CipherMode mode, const PatternSpec& pattern);
+  ~EncryptionScheme();
+  static EncryptionScheme unencrypted();
+  bool is_encrypted() const;
+
+  CipherMode mode;
+  PatternSpec pattern;
+};
+
+inline EncryptionScheme::PatternSpec::PatternSpec()
+    : encrypt_blocks(0), skip_blocks(0) {
+}
+
+inline EncryptionScheme::PatternSpec::PatternSpec(uint32_t encrypt_blocks,
+                                                  uint32_t skip_blocks)
+    : encrypt_blocks(encrypt_blocks), skip_blocks(skip_blocks) {
+}
+
+inline EncryptionScheme::PatternSpec::~PatternSpec() {}
+
+inline bool EncryptionScheme::PatternSpec::IsInEffect() const {
+  return encrypt_blocks != 0 && skip_blocks != 0;
+}
+
+inline EncryptionScheme::EncryptionScheme()
+    : mode(kCipherModeUnencrypted), pattern() {
+}
+
+inline EncryptionScheme::EncryptionScheme(CipherMode mode)
+    : mode(mode), pattern() {
+}
+
+inline EncryptionScheme::EncryptionScheme(CipherMode mode,
+                                          const PatternSpec& pattern)
+    : mode(mode), pattern(pattern) {
+}
+
+inline EncryptionScheme::~EncryptionScheme() {}
+
+inline EncryptionScheme EncryptionScheme::unencrypted() {
+  return EncryptionScheme(kCipherModeUnencrypted);
+}
+
+inline bool EncryptionScheme::is_encrypted() const {
+  return mode != kCipherModeUnencrypted;
+}
+
+// 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;
+
   // Stream id.
   StreamId id;
   // Audio codec.
@@ -114,8 +195,8 @@ 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()
@@ -124,13 +205,16 @@ 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() {
 }
 
+inline bool AudioConfig::is_encrypted() const {
+  return encryption_scheme.is_encrypted();
+}

[xhwang, 2016/03/03 22:33:00]

nit: you can implement this in line 182 directly.

[dougsteed, 2016/03/04 19:07:29]

Done.

+
 // TODO(erickung): Remove constructor once CMA backend implementation does't
 // create a new object to reset the configuration and use IsValidConfig() to
 // determine if the configuration is still valid or not.
@@ -138,6 +222,8 @@ struct VideoConfig {
   VideoConfig();
   ~VideoConfig();
 
+  bool is_encrypted() const;
+
   // Stream Id.
   StreamId id;
   // Video codec.
@@ -150,21 +236,24 @@ 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() {
 }
 
+inline bool VideoConfig::is_encrypted() const {
+  return encryption_scheme.is_encrypted();
+}

[xhwang, 2016/03/03 22:33:00]

ditto

[dougsteed, 2016/03/04 19:07:29]

Done.

+
 // TODO(erickung): Remove following two inline IsValidConfig() functions. These
 // are to keep existing CMA backend implementation consistent until the clean up
 // is done. These SHOULD NOT be used in New CMA backend implementation.