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<task id="GUID-2A69B0EE-FA13-49C3-B4FE-50D0910FA37D" xml:lang="en"><title>Processing

Key Stream</title><shortdesc>The <codeph>CKeyStreamDecoder</codeph> class provides an interface

for initializing key stream decoders and process a key stream.</shortdesc><prolog><metadata><keywords/></metadata></prolog><taskbody>

<context id="GUID-BFEED1F1-D00C-4E4A-B14E-8F60842A5F13">       <p>Follow the steps below to process a Key stream:</p>   

 </context>

stream decoder using <xref href="GUID-EE67D14D-1011-3B27-ADEC-C6C192339903.dita#GUID-EE67D14D-1011-3B27-ADEC-C6C192339903/GUID-F8F59778-6554-35A0-A2AD-DD689A89664D"><apiname>CKeyStreamDecoder::NewLC()</apiname></xref> to launch

a streaming agent. </cmd>

<info>           <p>When a key stream decoder is initialized, a streaming

agent that can handle the requested stream data is identified and launched.

Get the required parameters as input for integrating with the with Session

Description Protocol (SDP) definition.</p>         </info>

</step>

<step id="GUID-FC110D39-02A7-4E47-8766-3C98619DA560"><cmd>Query attributes

from the server using <xref href="GUID-EE67D14D-1011-3B27-ADEC-C6C192339903.dita#GUID-EE67D14D-1011-3B27-ADEC-C6C192339903/GUID-9F2F3999-FC78-3489-9A6A-FFE01F73E608"><apiname>CKeyStreamDecoder::GetStringAttributeL()</apiname></xref> and <xref href="GUID-EE67D14D-1011-3B27-ADEC-C6C192339903.dita#GUID-EE67D14D-1011-3B27-ADEC-C6C192339903/GUID-4E8A180B-EF34-3714-A58B-4CC7906D4BA3"><apiname>CKeyStreamDecoder::GetAttributeL()</apiname></xref>. </cmd>

<info><p>These methods provides information about a broadcaster or content

provider and recording right indicating whether a stream can be recorded.</p></info>

</step>

<step id="GUID-81A63AB2-E777-43F9-AA61-40BA91253484"><cmd>Record the stream

data using <xref href="GUID-EE67D14D-1011-3B27-ADEC-C6C192339903.dita#GUID-EE67D14D-1011-3B27-ADEC-C6C192339903/GUID-676470BD-41BC-3958-874D-40161B3895E1"><apiname>CKeyStreamDecoder::CreateImportSessionLC()</apiname></xref> to

check for post-acquisition rights. </cmd>

<info><p>If the rights object does not match with the recording rights, the

request fails and returns an error. </p></info>

</step>

</steps>

<example><p><b>Initializing key stream decoder</b></p><p>The following code

segment shows initializing a key stream decoder and querying attributes from

the server. </p><p> <b>Note</b>: The key stream decoder needs to remain active,

to process a key stream. </p><codeblock id="GUID-45178C59-4E22-5D1F-BAFF-61F7AED55D48" xml:space="preserve">

/* In this code sample, a key stream decoder is created to decode a key stream which 

   is protected by IPSec. Create a protected stream descriptor for IPSec.

   serverAddr => source connection address (content distributor in real case). 

   This address can be extracted from the SDP (Session Description Protocol).

   It is assumed that the client has already received this object.

   clientAddr => target connection address (device in real case).

*/

CProtectedStreamDesc *protectedStreamDesc = CIpSecProtectedStreamDesc::NewLC(serverAddr, clientAddr);

/* The relevant media field for the key stream (CSdpMediaField* keyStreamSDPDesc) is 

  extracted from the SDP (CSdpDocument* sdpDocument).

   ......

   Now create the key stream decoder by using the protected stream descriptor, the key stream media 

   field, and the whole SDP object. 

*/

CKeyStreamDecoder *keyStreamDecoder = CKeyStreamDecoder::NewLC(protectedStreamDesc, keyStreamSDPDesc, 

 sdpDocument);

Cleanupstack::PopAndDestroy(protectedStreamDesc);

/*If this section of code is reached, the key stream decoder is initialized correctly. If the user has rights to view the stream, the content 

            will be decrypted.

*/</codeblock><p>The following sequence of events occur in the back-end: </p><ul>

<li><p>In case of an authenticated user of the service, the streaming agent

loads the key stream. This creates a key stream decoder object. </p></li>

<li><p>The streaming agent starts a new processing task to decrypt the protected

stream data. For example, the key processing task for IPSec is to decrypt

Short Term Key Message (STKM) received as the key stream, and extract the

corresponding cryptographic context. </p></li>

</ul><note>s<ul>

<li id="GUID-08F29A6F-B8ED-5D19-A8B1-D2F25FDD82E5"><p>The key stream object

must be kept alive while receiving the key stream and decrypting the protected

streamed data. </p> </li>

<li id="GUID-B6FE0479-9679-536A-ADF7-1C7861E8EE4B"><p>If the user is not authenticated,

(for example, no rights for a specific pay-per-view program), cryptographic

context will not be set. </p> </li>

</ul></note><p><b>Querying for protected stream content</b></p><p>Query the

streaming agent to get information about the protected stream content, using

the created key stream decoder object. </p> <p>The following code snippet

shows an example for querying the playability of the content: </p> <codeblock id="GUID-8F515267-8EC1-55E6-B571-C25EFEDB66CC" xml:space="preserve">TBool playable = EFalse;

keyStreamDecoder->GetAttributeL(ECanPlay, playable);

// When the protected key stream receiving has finished or stopped, the key decoder object is destroyed.

Cleanupstack::PopAndDestroy(keyStreamDecoder);</codeblock><p><b>Recording

protected stream content</b> </p> <p>The following code snippet shows an example

of recording protected streamed content with post-acquisition rights. </p> <codeblock id="GUID-17747B2A-4E98-5999-94ED-53225D6717B7" xml:space="preserve">// Generate a protected key stream description for IPSec

CProtectedStreamDesc *protectedStreamDesc = CIpSecProtectedStreamDesc::NewLC(serverAddr, clientAddr);

// Create a key stream decoder 

CKeyStreamDecoder *keyStreamDecoder = CKeyStreamDecoder::NewLC(protectedStreamDesc, keyStreamSDPDesc,

 sdpDocument);

//Check whether the content is recordable

TBool value = EFalse;

keyStreamDecoder->GetAttributeL(ECanExport, value);

if(!value)

    {

    User::Leave(KErrCANotSupported);

    }

/* Get an import handle to record the protected streamed data in 3GPP video format

   By using the import handle, the streamed content will be recorded as protected together

   with its post-acquisition Rights Object. After importing, the recorded content is reached

   according to the restrictions defined in the post-acquisition Rights Object.

*/

CImportFile* import = keyStreamDecoder->CreateImportSessionLC(_L8("video/3gpp")); 

TPtr8 decryptedContent;

 do

    {

    // Decrypt the protected streamed content and assign to decryptedContent pointer.

    import->WriteData(decryptedContent);

    } while (decryptedContent);

// Import has been completed.

TFileName fileName;

TInt err = import->WriteDataComplete();

while (err == KErrCANewFileHandleRequired)              

     {

     err = ProvideNewOutputFileL(*import, fileName);

     if(err == KErrNone)

         {

         err = import->WriteDataComplete();

         }

     }

User::LeaveIfError(err);

</codeblock> </example>

</taskbody><related-links>

<link href="GUID-6AEA1BCF-EF19-5F6A-9452-E1149C949727.dita"><linktext>Using Streaming

CAF</linktext></link>

</related-links></task>