An Introduction to MPEG Audio.

by Davide Cilano

"NOTE BY THE EDITORS: This introduction to MPEG Audio is due to Davide Cilano, who wrote it in Italian. Denis Baggi has been so kind to translate it in English in a very short time. It consists of three chapters: a) an introduction to MPEG Audio coding; b) a survey of MPEG Audio syntactics; c) a tutorial on audio perceptive models. It is highly recommended to read this tutorial before considering the official specification of the MPEG Audio standard."

INDEX

• 1. ENCODING MPEG_AUDIO
  • 1.1. Compressed Encoding
  • 1.2. Redundancy and Irrelevance
  • 1.3. MPEG_Audio Encoding
    • 1.3.1. Introduction
    • 1.3.2. Encoding and Frames
    • 1.3.3. Frequency Representation
    • 1.3.4. Storage
    • 1.3.5. Decoding
  • 1.4. Characteristics
    • 1.4.1. Layer
    • 1.4.2. Sampling Frequencies
    • 1.4.3. Modality
    • 1.4.4. Bit Rate
  • 1.5. Data Structures Layer II
    • 1.5.1. Bit Allocation
    • 1.5.2. Scaling Factors
    • 1.5.3. SSFEI (Structure of Scaling Factors for Encoding on Intervals)
    • 1.5.4. The Samples
    • 1.5.5. Observations on Data Structures
  • 1.6. The Encoded Sequence Layer II
    • 1.6.1. Frame
    • 1.6.2. Header
    • 1.6.3. CRC [Cyclic Redundancy Code]
    • 1.6.4. Auxiliary Data (Ancillary)
    • 1.6.5. Syntax
  • 1.7. Evaluation of the Encoding
  • 1.8. Possible Applications
  • 1.9. An Application: DAB
    • 1.9.1. Characteristics of DAB
• 2. TECHNICAL SPECIFICATION OF MPEG_AUDIO
  • 2.1. Introduction
  • 2.2. Bibliography for Technical References
  • 2.3. Technical Glossary MPEG_Audio
  • 2.4. Encoding Process Layer II
    • 2.4.1. Flow Diagram
    • 2.4.2. Input High Pass Filter
    • 2.4.3. Filter Bank for Analysis
    • 2.4.4. FFT (Fast Fourier Transform)
    • 2.4.5. Psychoacoustical Model
    • 2.4.6. Encoding of Scaling Factors
    • 2.4.7. Computation of the Structure of Scaling Factors for Encoding on Intervals (SSFEI)
    • 2.4.8. Dynamic bit Allocation
      • 2.4.8.1. Flow Diagram
    • 2.4.9. Normalization and Quantization of Frequency Samples
    • 2.4.10. Error Protection
  • 2.5. Decoding Process Layer II
    • 2.5.1. Flow Diagram
    • 2.5.2. Frame Synchronization
    • 2.5.3. Header Decoding
    • 2.5.4. CRC Error Decoding
    • 2.5.5. Bit Allocation Decoding
    • 2.5.6. SSFEI Decoding
    • 2.5.7. Scaling Factors Decoding
    • 2.5.8. Sample de-quantization
    • 2.5.9. Sample de-normalization
    • 2.5.10. Subband Synthesis Filter
• 3. PERCEPTIVE MODELS
  • 3.1. Introduction
  • 3.2. Psychoacoustical Model
    • 3.2.1. Computational Algorithm
      • 3.2.1.1. FFT
      • 3.2.1.2. Determination of the Sound Pressure Level (SPL) of the signal
      • 3.2.1.3. Comparison with the threshold for no signal (static)
      • 3.2.1.4. Identification of Tonal and Non-tonal Components
        • 3.2.1.4.1. Local Maximum
        • 3.2.1.4.2. Tonal component
        • 3.2.1.4.3. Non-tonal component
      • 3.2.1.5. Selection of relevant Tonal and Non-tonal Components
      • 3.2.1.6. Computation of the individual Masking Threshold
      • 3.2.1.7. Computation of the Global Masking Threshold
      • 3.2.1.8. Determination of the minimal Masking Threshold
      • 3.2.1.9. Computation of the ratio Signal-to-Mask
    • 3.2.2. Accuracy of the Model
  • 3.3. Notes on Psychoacoustical Model
  • 3.4. Relation among SMR, SNR and MNR
  • 3.5. Results

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