ILMKlvBuilder Interface

 

The ILMKlvBuilder interface is provided by the LEAD MPEG-2 Transport Multiplexer to simplify the task of parsing KLV data. It can be obtained from the multiplexer by reading the ILMMpg2MxT::KlvBuilder property.

 

Data types:

 

typedefenum Mpg2MxT_SearchKey
{
   Mpg2MxT_SearchKey_Exact = 1,           /* Find only the exact key. The key version number must match. */
   Mpg2MxT_SearchKey_AnyVersion = 2,      /* Ignore the version number when doing the search. */
   Mpg2MxT_SearchKey_DesignatorOnly = 3,  /* Find the key by the designator only. Ignore the key representation and version number */
} Mpg2MxT_SearchKey;

 

typedefenum Mpg2MxT_Errors
{
   Mpg2MxT_E_KEY_NOT_FOUND = 0x80050010,    /* The KLV data was not found */
   Mpg2MxT_E_BAD_KEY = 0x80050011,          /* The KLV key is bad */
} Mpg2MxT_Errors;

 

Interface Properties:

 

Type

Property name

Description

long

Count

The number of complete top-level KLV keys contained in the internal interface buffer. An incomplete KLV key will not be included in the count.

 

Interface Methods:

 

HRESULT AddData(VARIANT Data, long lDataLengh);

Parameters

Data

Variant containing the private data.

DataLength

The size of data contained in Data.

Description

Use this method to begin building private data containing KLV packets. It is particularly useful from ILMMpgDmxCallback::DataAvailable when processing a source file containing KLV data. Build up the KLV data using this method and then edit the individual keys afterwards. This method appends the supplied data to the internal buffer. You should call the Clear method to restart the process. The Data parameter must contain a pointer to a byte array. The AddData method uses the smaller of the DataLength parameter and the actual array size.

Returns

S_OK if successful, < 0 if an error occurred.

Common error codes:

E_POINTER                  [0x80004003] Data is NULL

E_INVALIDARG             [0x80070057] Data is not a byte array variant

 

HRESULT CreateSubBuilder(ILMKlvBuilder** ppBuilder);

Parameters

ppBuilder

A pointer to a location to store a new builder interface pointer.

Description

Creates an independent builder for constructing subkeys.

Returns

S_OK if successful, < 0 if an error occurred.

Common error codes:

Value

Meaning

E_POINTER

[0x80004003] ppBuilder is NULL

 

HRESULT DeleteKey(long keyIndex);

Parameters

keyIndex

The index of the key to delete. The index is 0-based, so allowed values are 0..Count &ndash; 1.

Description

Deletes an existing key.

Returns

S_OK if successful, < 0 if an error occurred.

Common error codes:

Value

Meaning

DISP_E_BADINDEX

[0x8002000B] keyIndex is invalid.

 

HRESULT FindKey(VARIANT KeyToFind, long searchFlags, VARIANT *pKey, VARIANT *pKeyData, long *pDataSize);

Parameters

KeyToFind

Variant describing which key to look for.

searchFlags

One of the flags in the Mpg2MxT_SearchKey enumeration. These flags tell the parser how whether the match should be exact or not.

pKey

Pointer to a VARIANT that will be updated with a key describing the data. The key will be a 16-byte array describing the variant data. This key tells you how to interpret the key data contained in pKeyData.

pKeyData

Pointer to a VARIANT that will be updated key data. The key data will be a byte array variant regardless of the real format of the key data.

pDataSize

Pointer to a long variable that will be updated with the number of bytes stored in pKeyData. This is the same as the size of the pKeyData variant.

Description

Use searchFlags to specify whether you require an exact match for the key for which you are looking. Possible values for searchFlags are:

Mpg2MxT_SearchKey_Exact

An exact match is required. All 16 bytes of the key must match.

Mpg2MxT_SearchKey_AnyVersion

For a match to be acceptable, all key bytes must match, with the exception of the version key (the 7th byte).

Mpg2MxT_SearchKey_DesignatorOnly

For a match to be acceptable, the key designator component must match. The key designator is stored in the last 8 bytes of the key.

This function goes through the top keys in the buffer and compares them with the key passed in KeyToFind. If the key from the buffer matches exactly or partially (if permitted by searchFlags), then the key found is stored in pKey, the key data is stored in pKeyData and the key length is stored in pDataSize.

Returns

S_OK if successful, < 0 if an error occurred.

Common error codes:

Value

Meaning

E_POINTER

[0x80004003] pKey, pKeyData or pDataSize is NULL.

Mpg2MxT_E_KEY_NOT_FOUND

[0x80050010] There is no key matching KeyToFind and searchFlags.

E_OUTOFMEMORY

[0x8007000E] Could not allocate memory for the pKey or pKeyData variants.

 

HRESULT FindKeyStr(BSTR KeyToFind, long searchFlags, VARIANT *pKey, VARIANT *pKeyData, long *pDataSize);

Parameters

KeyToFind

String describing which key to look for.

searchFlags

One of the flags in the Mpg2MxT_SearchKey enumeration. These flags tell the parser whether the match should be exact or not.

pKey

Pointer to a VARIANT that will be updated with a key describing the data. The key will be a 16-byte array describing the variant data. This key tells you how to interpret the key data contained in pKeyData.

pKeyData

Pointer to a VARIANT that will be updated key data. The key data will be a byte array variant regardless of the real format of the key data.

pDataSize

Pointer to a long variable that will be updated with the number of bytes stored in pKeyData. This is the same as the size of the pKeyData variant.

Description

This method works exactly like FindKey, except that the key to search for is passed as a string, rather than a VARIANT.

KeyToFind is a string containing a hexadecimal representation of the bytes in the key. Each byte should be represented by two hexadecimal digits. Each digit can be:

Space characters are ignored. For example, &ldquo;06 0E 2B 34 01 0101 04 07 02 01 0101 05 00 00&rdquo; is equivalent to &ldquo;060E2B34010101040702010101050000&rdquo;.

For more information on each parameter, see the description for FindKey.

Returns

S_OK if successful, < 0 if an error occurred.

Common error codes:

Value

Meaning

E_POINTER

[0x80004003] pKey, pKeyData or pDataSize is NULL.

Mpg2MxT_E_KEY_NOT_FOUND

[0x80050010] There is no key matching KeyToFind and searchFlags.

E_OUTOFMEMORY

[0x8007000E] Could not allocate memory for the pKey or pKeyData variants.

Mpg2MxT_E__BAD_KEY

[0x80050011] The key string is invalid: the key string should contain a hexadecimal representation of a 16-byte value, with 2 digits per byte (32 digits total).

 

HRESULT GetData(VARIANT* pData);

Parameters

Data

Pointer to a variant that is filled with a byte array copy of the current data.

Description

Creates a copy of the current data.

Returns

S_OK if successful, < 0 if an error occurred.

Common error codes:

E_POINTER                  [0x80004003] Data is NULL

E_OUTOFMEMORY      [0x80070057] The array for the copy could not be allocated.

  

HRESULT GetKey(long keyIndex, VARIANT *pKey, VARIANT *pKeyData, long *pDataSize);

 Parameters

keyIndex

The index of the key to retrieve. The index is 0-based, so allowed values are 0..Count &ndash; 1

pKey

Pointer to a VARIANT that will be updated with a key describing the data. The key will be a 16-byte array describing the variant data. This key tells you how to interpret the key data contained in pKeyData.

pKeyData

Pointer to a VARIANT that will be updated key data. The key data will be a byte array variant regardless of the real format of the key data.

pDataSize

Pointer to a long variable that will be updated with the number of bytes stored in pKeyData. This is the same as the size of the pKeyData variant.

 Description

Use this method to enumerate all the keys contained in a private data sample. This method enumerates all the data passed to AddData.

The method allocates data for the pKey and pKeyData variants. You should make sure you free the memory allocated in these variants if your programming language does not do so automatically. For example, VB automatically frees this memory, but C/C++ does not. In C++, you free the variant memory by calling VariantClear. Please consult the documentation for your programming language for more information on how to free the variant data.

You should examine pKey to find out how to interpret the key data. The IKlvBuilder will not interpret the key data for you. There is not a single document describing all the KLV keys that you might find in a stream. You will find various documents describing certain lists of currently defined keys. But each company that generates MPEG-2 transport streams or files might write their own internal keys in a private data stream. At the time of writing this documentation, the following documents contained information on KLV keys and how to interpret their content:

Based on information on this and other documents that you might find, you should interpret the key data accordingly. For example:

Key: 06 0E 2B 34 01 0101 04 07 02 01 0101 05 00 00

Is a &ldquo;User Defined Time Stamp (microseconds since 1970)&rdquo; in msb bit order and that the key should be 8 bytes long. In this case, you should verify that *pDataSize is 8. If *pDataSize is 8, you should convert the 8-byte array into a 64-bit unsigned integer (or a double floating point if your programming language does not support 64-bit integers). You would then convert the 64-bit value into a date and time by counting the microseconds since 1970.

 Returns

S_OK if successful, < 0 if an error occurred.

 Common error codes:

Value

Meaning

DISP_E_BADINDEX

[0x8002000B] keyIndex is invalid (< 0).

E_POINTER

[0x80004003] pKey, pKeyData or pDataSize is NULL.

Mpg2MxT_E_KEY_NOT_FOUND

[0x80050010] The key was not found (keyIndex >= Count).

E_OUTOFMEMORY

[0x8007000E] Could not allocate memory for the pKey or pKeyData variants.

  

HRESULT InsertKey(long keyIndex, VARIANT Key, VARIANT KeyData, long DataSize);

 Parameters

keyIndex

The index of the keys insertion point. The index is 0-based, so allowed values are 0..Count &ndash; 1. However, a special value of -1 will append the key to the end of the current data.

Key

VARIANT a key describing the data. The key will be a 16-byte array describing the variant data. This key tells you how to interpret the key data contained in KeyData.

KeyData

VARIANT containing key data. The key data will be a byte array variant regardless of the real format of the key data.

DataSize

Long variable describing the number of bytes stored in KeyData. This is the same as the size of the KeyData variant.

 Description

Inserts a new key.

 Returns

S_OK if successful, < 0 if an error occurred.

Common error codes:

Value

Meaning

DISP_E_BADINDEX

[0x8002000B] keyIndex is invalid.

E_OUTOFMEMORY

[0x8007000E] Could not allocate memory for the new data.

  

HRESULT SetKey(long keyIndex, VARIANT Key, VARIANT KeyData, long DataSize);

Parameters

keyIndex

The index of the key to replace. The index is 0-based, so allowed values are 0..Count &ndash; 1

Key

VARIANT a key describing the data. The key will be a 16-byte array describing the variant data. This key tells you how to interpret the key data contained in KeyData.

KeyData

VARIANT containing key data. The key data will be a byte array variant regardless of the real format of the key data.

DataSize

Long variable describing the number of bytes stored in KeyData. This is the same as the size of the KeyData variant.

Description

Replaces an existing key.

Returns

S_OK if successful, < 0 if an error occurred.

Common error codes:

Value

Meaning

DISP_E_BADINDEX

[0x8002000B] keyIndex is invalid.

E_OUTOFMEMORY

[0x8007000E] Could not allocate memory for the new data.