KLVLib Documentation

Introduction

KLV (Key-Length-Value) is a data encoding standard used for binary data byte-packing and metadata embedding into video feeds. Data is encoded into Key-Length-Value triplets, where Key identifies the data, Length specifies the data's length, and Value is the data itself. It is defined in SMPTE 336M-2007 (Data Encoding Protocol Using Key-Length Value), approved by the Society of Motion Picture and Television Engineers. KLV encoding protocol defines a data structure which is independent of the application or transportation method used. KLV encoder C++ library allows seamless integration at the encoding/streaming side, while KLV decoder module may be used at the client side in order to extract encoded data.

Using KLVLib for encoding/decoding metadata for Unmanned Air System (UAS)

Unmanned Air Systems use two types of KLV encoded metadata. Universal Data Set (UDS) - the 16-byte key, basic encoding rules (BER) formatted length, and data value is appropriate for applications where bandwidth isn't a concern. However, transmitting the 16-byte universal key quickly uses up the available bandwidth. UAS airborne platforms use a wireless communications channel where the bandwidth allocated for metadata is limited. Because of the bandwidth disadvantages of using a Universal Data Set, it is more desirable to use a Local Data Set for transmission over a UAS Datalink. Local Data Set can use a 1, 2 or 4-byte key with a 1, 2, 4-byte, or BER encoded length. For more info about KLV use in UAS application see KLV in UAS applications

KLVLib supports BER Short Form Length Encoding and BER Long Form Length Encoding

Components

KLVLib contains classes and functions for Klv Data manipulation.

• IKlvItem - a base class that implements a Klv functionality.
• IKlvEncoder - a class that implements encoding of Klv byte array containing multiple KlvItems.
• IKlvDecoder - a class that implements decoding functionality ( byte array parsing and KlvItem list creation).
• Helper functions Helper functions

Diagrams

Sequence diagrams

Getting started with KlvLib

KlvLib SDK provides examples with source code to help you get started using the library. Here is a brief demo on how to use KlvLib for metadata encoding (LDS).

• Add KlvLib.lib and make sure you have KlvLib.dll accessible by your code.
• Include "IKlvLib.h" file.

  #include "IEG0601Conv.h"

• Create KlvEncoder instance.

  // Create STANAG 4609 KLV encoder
  IKlvEncoder* klvEncoder = CreateKlvEncoder();

• Set "Outer Key and checksum key

  // Set outer key. We use ASCII string for this example
  klvEncoder->SetOuterKey("060E2B34020B01010E01030101000000");
  
  // Set checksum key
  klvEncoder->SetCheckSumKey("01");       

• Add few Klv items

  // Key 02       | A timestamp.  Unix Time Stamp - Microseconds L = 8. Mon Jan 12 2009 22:08:22 (UTC) 00 04 60 50 58 4E 01 80
  unsigned __int64 val_64 = 1231798102000000; // After endian swap - { 0x00, 0x04, 0x60, 0x50, 0x58, 0x4E, 0x01, 0x80 };          
  char key = 2;
  klvEncoder->AddKlvItem(key, val_64);
  
  
  // Key 05   | Add Platform Heading Angle    | 0x71C2        | 159.9744 Degrees                                  
  unsigned short val_16 = 0x71C2; 
  key = 5;
  klvEncoder->AddKlvItem(key, val_16);

• Encode the data

  // Encode and return an encoded byte array
  char*   pEncChunk = klvEncoder->Encode(encodedLength);

• Use the data and delete the encoder

  // Use the results
  if( encodedLength )
  {
          // Do something with the data 
          memcpy(klvBuffer, pEncChunk, encodedLength);            
  }       
  
  // Delete the KlvEncoder and deallocate memory
  delete klvEncoder;

Example

For more info see Using KlvLib sample or Using KlvLib (16 bytes Keys) sample