Merge "Document CryptoInfo Settings for CENC 2016 & HLS Audio" into pi-dev (889da15d) · Commits · e / os / android_frameworks_base

media/java/android/media/MediaCodec.java

+70 −25

Original line number	Diff line number	Diff line
		@@ -2359,17 +2359,61 @@ final public class MediaCodec {
		public static final int CRYPTO_MODE_AES_CBC = 2;

		/**
		* Metadata describing the structure of a (at least partially) encrypted
		* input sample.
		* A buffer's data is considered to be partitioned into "subSamples",
		* each subSample starts with a (potentially empty) run of plain,
		* unencrypted bytes followed by a (also potentially empty) run of
		* encrypted bytes. If pattern encryption applies, each of the latter runs
		* is encrypted only partly, according to a repeating pattern of "encrypt"
		* and "skip" blocks. numBytesOfClearData can be null to indicate that all
		* data is encrypted. This information encapsulates per-sample metadata as
		* outlined in ISO/IEC FDIS 23001-7:2011 "Common encryption in ISO base
		* media file format files".
		* Metadata describing the structure of an encrypted input sample.
		* <p>
		* A buffer's data is considered to be partitioned into "subSamples". Each subSample starts with
		* a run of plain, unencrypted bytes followed by a run of encrypted bytes. Either of these runs
		* may be empty. If pattern encryption applies, each of the encrypted runs is encrypted only
		* partly, according to a repeating pattern of "encrypt" and "skip" blocks.
		* {@link #numBytesOfClearData} can be null to indicate that all data is encrypted, and
		* {@link #numBytesOfEncryptedData} can be null to indicate that all data is clear. At least one
		* of {@link #numBytesOfClearData} and {@link #numBytesOfEncryptedData} must be non-null.
		* <p>
		* This information encapsulates per-sample metadata as outlined in ISO/IEC FDIS 23001-7:2016
		* "Common encryption in ISO base media file format files".
		* <p>
		* <h3>ISO-CENC Schemes</h3>
		* ISO/IEC FDIS 23001-7:2016 defines four possible schemes by which media may be encrypted,
		* corresponding to each possible combination of an AES mode with the presence or absence of
		* patterned encryption.
		*
		* <table style="width: 0%">
		* <thead>
		* <tr>
		* <th> </th>
		* <th>AES-CTR</th>
		* <th>AES-CBC</th>
		* </tr>
		* </thead>
		* <tbody>
		* <tr>
		* <th>Without Patterns</th>
		* <td>cenc</td>
		* <td>cbc1</td>
		* </tr><tr>
		* <th>With Patterns</th>
		* <td>cens</td>
		* <td>cbcs</td>
		* </tr>
		* </tbody>
		* </table>
		*
		* For {@code CryptoInfo}, the scheme is selected implicitly by the combination of the
		* {@link #mode} field and the value set with {@link #setPattern}. For the pattern, setting the
		* pattern to all zeroes (that is, both {@code blocksToEncrypt} and {@code blocksToSkip} are
		* zero) is interpreted as turning patterns off completely. A scheme that does not use patterns
		* will be selected, either cenc or cbc1. Setting the pattern to any nonzero value will choose
		* one of the pattern-supporting schemes, cens or cbcs. The default pattern if
		* {@link #setPattern} is never called is all zeroes.
		* <p>
		* <h4>HLS SAMPLE-AES Audio</h4>
		* HLS SAMPLE-AES audio is encrypted in a manner compatible with the cbcs scheme, except that it
		* does not use patterned encryption. However, if {@link #setPattern} is used to set the pattern
		* to all zeroes, this will be interpreted as selecting the cbc1 scheme. The cbc1 scheme cannot
		* successfully decrypt HLS SAMPLE-AES audio because of differences in how the IVs are handled.
		* For this reason, it is recommended that a pattern of {@code 1} encrypted block and {@code 0}
		* skip blocks be used with HLS SAMPLE-AES audio. This will trigger decryption to use cbcs mode
		* while still decrypting every block.
		*/
		public final static class CryptoInfo {
		/**
		@@ -2377,11 +2421,13 @@ final public class MediaCodec {
		*/
		public int numSubSamples;
		/**
		* The number of leading unencrypted bytes in each subSample.
		* The number of leading unencrypted bytes in each subSample. If null, all bytes are treated
		* as encrypted and {@link #numBytesOfEncryptedData} must be specified.
		*/
		public int[] numBytesOfClearData;
		/**
		* The number of trailing encrypted bytes in each subSample.
		* The number of trailing encrypted bytes in each subSample. If null, all bytes are treated
		* as clear and {@link #numBytesOfClearData} must be specified.
		*/
		public int[] numBytesOfEncryptedData;
		/**
		@@ -2400,35 +2446,34 @@ final public class MediaCodec {
		public int mode;

		/**
		* Metadata describing an encryption pattern for the protected bytes in
		* a subsample. An encryption pattern consists of a repeating sequence
		* of crypto blocks comprised of a number of encrypted blocks followed
		* by a number of unencrypted, or skipped, blocks.
		* Metadata describing an encryption pattern for the protected bytes in a subsample. An
		* encryption pattern consists of a repeating sequence of crypto blocks comprised of a
		* number of encrypted blocks followed by a number of unencrypted, or skipped, blocks.
		*/
		public final static class Pattern {
		/**
		* Number of blocks to be encrypted in the pattern. If zero, pattern
		* encryption is inoperative.
		* Number of blocks to be encrypted in the pattern. If both this and
		* {@link #mSkipBlocks} are zero, pattern encryption is inoperative.
		*/
		private int mEncryptBlocks;

		/**
		* Number of blocks to be skipped (left clear) in the pattern. If zero,
		* pattern encryption is inoperative.
		* Number of blocks to be skipped (left clear) in the pattern. If both this and
		* {@link #mEncryptBlocks} are zero, pattern encryption is inoperative.
		*/
		private int mSkipBlocks;

		/**
		* Construct a sample encryption pattern given the number of blocks to
		* encrypt and skip in the pattern.
		* Construct a sample encryption pattern given the number of blocks to encrypt and skip
		* in the pattern. If both parameters are zero, pattern encryption is inoperative.
		*/
		public Pattern(int blocksToEncrypt, int blocksToSkip) {
		set(blocksToEncrypt, blocksToSkip);
		}

		/**
		* Set the number of blocks to encrypt and skip in a sample encryption
		* pattern.
		* Set the number of blocks to encrypt and skip in a sample encryption pattern. If both
		* parameters are zero, pattern encryption is inoperative.
		*/
		public void set(int blocksToEncrypt, int blocksToSkip) {
		mEncryptBlocks = blocksToEncrypt;