Audio%20Coding - PowerPoint PPT Presentation

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Audio%20Coding

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Audio Coding MPEG1 Layers I, II, III MPEG2 MPEG4 Sherida Subrati Anthony Caliendo – PowerPoint PPT presentation

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Title: Audio%20Coding


1
Audio Coding
  • MPEG1 Layers I, II, III
  • MPEG2
  • MPEG4

Sherida Subrati Anthony Caliendo
2
Overview
  • Explanation of Codecs
  • MPEG1 Layer I, II, III (Differences)
  • MPEG2 Basic Overview
  • MPEG4 Possible Applications
  • Applications Sound Samples Used
  • Results Explanation
  • File Size, Bitrate, Quality
  • Waveform Comparison
  • Summary Questions

3
Sub-Band Coding Overview
  • Size of sub-bands varies
  • Varying application of psychoacoustic model

4
MPEG1 Layer I II
  • Time Frequency Mapping
  • Polyphase Filter Bank
  • 32 Equal Bands
  • Psychoacoustic Model
  • 512-point FFT 1024-point FFT respectively
  • Tonal Noise Masking
  • Quantizer
  • Scale Factor 6 bits
  • Layer II Allows 3 successive scale factors
    uses 1-3 depending on how much they differ

5
MPEG1 Layer I II Diagram
Images from Peter Noll MPEG Digital Audio Coding
Standards
6
MPEG1 Layer III
  • Time Frequency Mapping
  • Switched Hybrid Filter Bank
  • 32 sub-bands further sub-divided using a6 or
    18-point DCT
  • Psychoacoustic Model
  • Variable FFT
  • Tonal Noise Masking
  • Quantizer
  • Non-uniform Scale Factors
  • Huffman Coding, Bit Reservoir, Iterative
    Analysis

7
MPEG1 Layer III Diagram
Images from Peter Noll MPEG Digital Audio Coding
Standards
8
MPEG2 General Overview
  • 5.1 Channel Support
  • Advanced Audio Coding (AAC)
  • Optional Preprocessing
  • Bit-stream Formatter
  • Prediction helps to optimize quantizer
  • Noiseless Coding
  • 3 Profiles
  • Main Variable length DCT, noiseless coding,
    etc.
  • Low Complexity No temporal noise shaping time
    domain prediction
  • Sampling Rate Scalability preprocessor allows
    for sampling rates of 6, 12, 18, 24 KHz

9
MPEG4 - General Overview
  • Consists of all previous MPEG iterations
  • Uses 3 Core Coders
  • Parametric coding for low bit rate speech
  • Analysis-by-synthesis for medium bit rates
  • Sub-band/Transform coding for high bit rates
  • Low Delay (LD) Encoding / Decoding
  • Quality Scalability

10
MPEG 4 - Diagram
11
Applications Sound Samples
  • Applications
  • AVI2MP.EXE
  • LAMEwin32
  • Nero MPEG4 AAC
  • Goldwave
  • Hardware
  • Pentium III 1.0 GHz
  • 512MB RAM
  • Win2K SP3
  • Sound Samples
  • PCM 16-bit Stereo 44.1 KHz
  • Clubbed to Death (Kurayamino Mix) Rob D
  • Man Who Sold The World - Nirvana
  • PCM 8-bit Mono 44.1Khz
  • Voice Sample

12
Results File size VS Bitrate
13
Results Encode Time VS Bitrate
14
Results Quality VS Bitrate
15
Sample Sounds
  • Music Sample
  • Original Sound
  • Sample 2 Play list
  • S2-M4LT-064S
  • S2-M4LT-080S
  • S2-M4LT-096S
  • Voice Sample
  • Original Sound
  • Sample 3 Play list
  • S3-M4LT-016M
  • S3-M4LT-024M
  • S3-M4LT-032M

16
Sample Waveforms S2-64
17
Sample Waveforms S2-128
18
Sample Waveforms S3-64
19
Sample Waveforms S3-96
20
Summary
  • MPEG1 Layers I, II have limited options are
    not size versus quality efficient
  • MPEG1 Layer III offers excellent quality at low
    rates but has large overhead
  • MPEG2 Much more comprehensive
  • MPEG4 Encompasses all previous iterations has
    new capabilities to increase its lifespan
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