Global Structure of Multimedia with Block Diagram

Introduction

Multimedia is the integration of multiple forms of media such as text, audio, video, graphics, and animation into a single interactive system to convey information effectively. The global structure of multimedia describes how various components work together to capture, process, store, communicate, and present media information to the end user.

Block Diagram of Global Structure of Multimedia

+------------------+
|   INPUT DEVICES  |
| (Keyboard, Mouse,|
|  Microphone,     |
|  Camera, Scanner,|
|  Tracker)        |
+--------+---------+
         |
         v
+------------------+       +---------------------+
|  PROCESSING      |<----->|   STORAGE MEDIUM    |
|  SYSTEM          |       | (Hard Disk, CD-ROM, |
| (CPU, Multimedia |       |  DVD, Cloud)        |
|  Software,       |       +---------------------+
|  Compression/    |
|  Decompression,  |
|  Authoring Tools)|
+--------+---------+
         |
         v
+------------------+       +---------------------+
|  COMMUNICATION / |<----->|  NETWORK/INTERNET   |
|  TRANSMISSION    |       | (Coaxial, Fiber,    |
|  MEDIUM          |       |  Wireless, TCP/IP)  |
+--------+---------+       +---------------------+
         |
         v
+------------------+
|  OUTPUT DEVICES  |
| (Monitor, Speaker|
|  Printer,        |
|  Projector)      |
+------------------+
         |
         v
+------------------+
|   END USER /     |
|   PERCEPTION     |
+------------------+

Detailed Explanation of Each Component

A. Perception Medium (Input Side)

Perception media help humans sense their environment. In a computer environment, humans receive information primarily through:

• Seeing: Text, images, and video
• Hearing: Music, noise, and speech

This defines what kind of input the system must capture and what output it must produce.

B. Presentation Medium (Input Devices)

Presentation media refer to the tools and devices for input and output of information.

Input devices include:

• Keyboard and Mouse for text and navigation input
• Microphone for capturing audio (a source of non-persistent continuous data)
• Camera/Webcam for capturing video and images
• Scanner Devices: Image scanners and photo CD devices support input and output of images and photographs. For high-quality publication work, a photo scanner is used.
• Recognition Devices: Recognizers such as the object-oriented character recognition engine AQUIRE are used in pen-based environments to recognize different media.
• Tracking Devices: Trackers report information about position, orientation, acceleration, and pressure using technologies like electromagnetic trackers and ultrasonic trackers.

C. Representation Medium (Processing System)

Representation media are defined by the internal computer representation of information. The question is how computer information is coded:

• Text and characters are coded as ASCII
• Images can be coded in JPEG format
• Audio and video use formats like MPEG

Processing includes:

1. Audio Support: Multiple-channel digital sound tracks are supported. In virtual reality entertainment, sound interaction occurs via a helmet, and stereo sound design is important.

2. Video Support: Video boards and digitizers aim toward high-resolution picture presentation. The ultimate goal is high resolution at a film rate of 60 frames per second or faster. An important capability is to provide a constant frame rate with a minimum of jitter.

3. Compression and Decompression: Since storage space requirements for uncompressed data are far larger than for compressed data, and transmission of uncompressed data over digital networks requires higher bandwidth, multimedia systems use compressed formats. The most important compression techniques are:

   • JPEG for single pictures
   • H.265 for video
   • MPEG for video and audio

4. Authoring Tools: An authoring system is a set of software tools for creating multimedia applications. A person who creates applications for multimedia integration is called an author, and the process is called authoring.

5. Multimedia Editors: Multimedia editors support the ability to manipulate multimedia documents that include structured text, bitmap images, graphics, video, and digitized voice. An example is BBN's Diamond Multimedia Editor.

6. Video Editors: Video editors are based on image editors for editing individual frames. They can combine several cuts into one sequence, adjust audio separately from video, and add video transition effects.

7. System Software and Libraries: The processing of continuous media is based on functions embedded into libraries provided with corresponding hardware. At the system level:

   • Data as Streams: A stream denotes the continuous flow of audio and video text, established between source(s) and sink(s). Operations such as play, fast forward, rewind, and stop can be performed. In Microsoft Windows, the Media Control Interface (MCI) provides the interface for processing multimedia data.
   • Data as Time Capsules: Each Logical Data Unit (LDU) carries its time capsule along with data type, actual value, and valid life span.

8. Toolkits: Toolkits are used to abstract from the actual physical layer, allow a uniform interface for communication with all different devices of continuous media, introduce the client-server paradigm, and hide process structures.

D. Storage Medium

Storage media refer to the data carriers that enable storage of information. Since multimedia files (especially audio and video) are very large, adequate storage is essential.

Examples include:

• Hard Disk Drive (HDD)
• CD-ROM
• DVD, Blu-ray
• USB drives
• Cloud Storage

Compression is critical here because uncompressed data requires far more storage space.

E. Transmission Medium / Communication

Transmission media are the different information carriers that enable continuous data transmission. The question is over which medium information will be transmitted:

• Wired: Coaxial cable, fiber optics
• Wireless: Free air (radio, Wi-Fi)

Information Exchange Medium combines both storage and transmission media for exchanging information between different places. An example is an electronic mailing system.

Media Communication denotes applications that exchange information over both storage and transmission media together, such as a video-on-demand service that both stores content on disk and streams it over a network to many users.

F. Output Devices and Perception (Closing the Loop)

The processed and transmitted media finally reaches the output devices shown at the bottom of the block diagram:

• Monitor / Display: Presents text, images, graphics, and video.
• Speaker: Presents audio and speech output.
• Printer: Produces a hard copy of text or images.
• Projector: Presents visual media to a larger audience.

The output devices convert the internal (representation medium) form of the data back into a perception medium the end user can see or hear, completing the loop shown in the block diagram: input devices capture perception media, the processing system represents and manipulates it, storage and transmission media move and hold it, and output devices turn it back into something the human senses can perceive.

Conclusion

The global structure of multimedia is best understood as a pipeline: input devices capture raw perceptual data (text, image, audio, video) from the user's environment; the processing system represents this data digitally, compresses it, and prepares it using authoring tools; storage media hold the data (compressed, to save space); transmission media carry it across networks when needed; and output devices finally convert the processed digital representation back into a form (sight, sound) that a human can perceive. Every stage in this pipeline, from the initial microphone or camera input all the way to the final speaker or monitor output, must cooperate to preserve the timing and synchronization that time-dependent media such as audio and video require, which is exactly what distinguishes a multimedia system from a system that merely stores separate, unrelated pieces of text, image, and sound.

Huffman Coding

Definition

Huffman coding is a lossless data compression technique and a type of entropy coding that assigns variable-length binary codes to input characters based on their frequency of occurrence. Characters that occur more frequently are assigned shorter codes, while characters that occur less frequently are assigned longer codes. This minimizes the total number of bits required to represent the data.

: "Run-length coding, Huffman coding, Arithmetic coding are entropy coding" and in JPEG entropy encoding, "Huffman coding is preferred as it is free."

Key Characteristics

• It is a lossless (hassless) compression method -- decompression regenerates data completely.
• It is based on the frequency/probability of characters in the data.
• It produces an optimal prefix code -- no code is a prefix of another code.
• It uses a binary tree structure called the Huffman Tree.

Huffman Coding Process (Algorithm)

The steps to build a Huffman code are:

Step 1: Count the frequency of each character in the input data.

Step 2: Create a leaf node for each character and insert all nodes into a min-priority queue (ordered by frequency, lowest first).

Step 3: While there is more than one node in the queue:

• Remove the two nodes with the lowest frequency (call them Left and Right).
• Create a new internal node with frequency = Left frequency + Right frequency.
• Assign the Left node as the left child and the Right node as the right child.
• Insert the new internal node back into the queue.

Step 4: The remaining single node is the root of the Huffman Tree.

Step 5: Assign binary codes by traversing the tree:

• Going Left = assign bit 0
• Going Right = assign bit 1

Step 6: The code for each character is the sequence of bits from the root to that leaf node.

Worked Example

Given Input String:

"AABBBCCDDDDEE"

Step 1: Calculate Frequencies

Total characters = 13

Step 2: Build Min-Priority Queue (sorted by frequency)

A(2), C(2), E(2), B(3), D(4)

Step 3: Build the Huffman Tree

Iteration 1: Pick two lowest: A(2) and C(2)

• Create internal node AC(4)
• Queue: E(2), B(3), AC(4), D(4)

    AC(4)
   /     \
 A(2)   C(2)

Iteration 2: Pick two lowest: E(2) and B(3)

• Create internal node EB(5)
• Queue: AC(4), D(4), EB(5)

    EB(5)
   /     \
 E(2)   B(3)

Iteration 3: Pick two lowest: AC(4) and D(4)

• Create internal node ACD(8)
• Queue: EB(5), ACD(8)

     ACD(8)
    /      \
  AC(4)   D(4)
  /   \
A(2) C(2)

Iteration 4: Pick two lowest: EB(5) and ACD(8)

• Create root node EBACD(13)
• Queue: EBACD(13) -- only one node remains, this is the root

          EBACD(13)
         /          \
       EB(5)        ACD(8)
      /    \        /    \
    E(2)  B(3)   AC(4)  D(4)
                 /    \
               A(2)  C(2)

Step 4 and 5: Assign Codes (Left = 0, Right = 1)

Traverse from root to each leaf:

Step 6: Calculate Compression

Total bits with Huffman coding:

Without Huffman coding (fixed 3-bit code for 5 characters):

• 13 characters x 3 bits = 39 bits

Compression achieved: 39 - 30 = 9 bits saved (approximately 23% compression)

Advantages of Huffman Coding

1. It is lossless -- original data is perfectly recovered.
2. It produces optimal prefix-free codes.
3. It is widely used in JPEG, MPEG, ZIP and other multimedia compression standards.
4. Frequently occurring symbols get shorter codes, reducing overall data size.

Summary

Huffman coding is a powerful entropy coding technique that exploits the statistical redundancy in the data by assigning shorter binary codes to more frequent characters and longer codes to rarer ones, while the prefix-free property of the resulting codes guarantees that the encoded bit stream can always be decoded unambiguously using the same binary tree that was built during encoding, without needing any separators between codes.