Academic year 2014-15

Voice and Audio Encoding Systems

Degree:	Code:	Type:
Bachelor's Degree in Computer Science	21484	Optional subject
Bachelor's Degree in Telematics Engineering	21764	Optional subject
Bachelor's Degree in Audiovisual Systems Engineering	21614	Compulsory subject, 3rd year

 

ECTS credits:

4

Workload:

100 hours

Trimester:

 

Department:	Dept. of Information and Communication Technologies
Coordinator:	Julio Carabias
Teaching staff:	Julio Carabias
Language:	Spanish (speech), English (material)
Timetable:
Building:	Communication campus - Poblenou

 

Introduction

This course is related to the digital coding of audio signals and it is designed for Audiovisuals Systems Engineering students.

This course is focus on the study of the most known methods for audio coding.

 

Prerequisites

The course requires previous knowledge of other courses in the degree including: Data Transmission and Coding (second year, Audiovisuals Systems Engineering), Signals and Systems (second year, Audiovisuals Systems Engineering), Speech Processing (second year, Audiovisuals Systems Engineering).

 

Associated competences

Competences to be worked during the course according to the degree description:

Cross-disciplinary competences

Specific competences

Instrumentals G1. Analysis and synthesis G2. Organization and planning G3. Application of knowledge in novel problems and situations G4. Information retrieval and management G5. Decision making G7. Oral and writting communication   Interpersonals G8. Team work Sistèmiques G11. Flexibility and creativity to apply knowledge to novel contexts G12. Ability for self-training

Specific from basic training B4 - INF / B4 - A. Complex variable functions B7 - INF / B7 - A. Fourier transforms and sampling theorem B8 - INF. Lineal and Time-Invariant systems and related functions B3-A. Differencial equations and partial derivatives. B5-A. Vectorial and numeric analysis. B9-A. A. Sound propagation, acoustics, and digital signal processing Related to Audio coding AU23. Decide best audio and music coding systems for a given application. AU8. Projects related to audio and video generation/recording. AU34. Audio and music recording, generation and production knowledge.  AU10. Understand problems related to room acoustics. AU11. Knowledge related to surround sound production.  AU12. Audiovisual projects production, postproduction and exhibition. AU14. Linear and non-linear problems optimization using numerical numbers. AU22. Basic mathematical knowledge related to audio and music coding. Advantages and drawbacks of each method.

 

 

 

Assessment

The evaluation is splitted between the three main activities of the course: theoretical concepts (T), seminars (S) and labs (L) as follows:

	Description	Timing	Recoverable
Writtent tests	Final exam (80% of T): the final exam includes all the course conceptual materia, including questions related to the labs.	End of term	Yes
Written products	Test (20% of T): partial exam of concepts, including questions related to the labs.	Middle of term	No
	Seminar activities (S)	Along the term	No
Practical work	Labs (L): submission of lab reports (30% of L) (individually or in couples) and an exam at the end of the term  (10% of L).	Along the term	No

 

Minimum requirements:

• T: concept evaluation. A minimum of 5/10 is required to pass the course.

• L: A minimum of 5/10 is required to pass the course.

The final mark is obtained through the following formula:

Nota Final = 0,5*T + 0,4*L + 0,1*S

 

Contents

The aim of this course is to introduce the methodology for coding and decoding of audio signals (speech, sound and music) to the student. More precisely, the student is aimed to learn theoretical and practical competences related to:

• Block scheme of a general audio and speech coding system.
• The human auditory system: Application to coding.
• Analysis:
  • Sound, speech and music analysis.
  • Cosine Discrete Transform.
  • Subbands analysis.
  • Bit allocation strategies.
• Time domain Coding.
  • PCM coding.
  • Predictive coding.
• Frequency domain Coding.
  • Audio MPEG-1, MPEG-2 y MPEG-2 AAC, MPEG-4.
  • Audio Dolby AC-3.
• Applications. Voice over IP.
• Current audio coding strategies.

 

Methodology

For this topic, there is a theory session, a seminar and a lab. During the theory session, the main concepts are presented to the whole class. The student should then review them with the help of the material provided by the teacher.

After that, a seminar session is planned, where the student will be solving some exercises and problems related to the theoretical concepts. This activity is carried out in small grups in an interactive way.

Finally, a practical session with computers is scheduled in order to solve, in couples, practical problems requiring algorithm implementations and practical work with sound and the proposed software.

 

	In-class activity			Hours for personal work Assessment activity
Topic	Full group	Medium group	Small group
1	1/2			2
2	1/2	1/2	1	3
3	1	1/2	1	7
4	2	2	2	10
5	2	1	1	7
6	1		1	7
7	1			5
8	1	1	1	8
Summary				8
Final exam preparation				7
Total:	18	5	8	64	Total: 100

 

Theory: 18 hours (9 sessions, 2 hours each).

• Lecture 1: Introduction
• Lecture 2: Quantization
  • Uniform Quantization
  • Non-uniform quantization
  • Vector Quantization
• Lecture 3: Entropy Coding applied to Audio
  • Huffmann
  • Arithmetic Coding
• Lecture 4: Time-Frequency Analysis and Synthesis.
  • Two-Band decomposition and perfect reconstruction
  • Quadrature Polyphase Filterbanks
  • Modified Discrete Transform (MDCT)
• Lecture 5: Psychoacoustics and Psychoacousitc Models of Perceptual Audio Codecs
  • Spectral Masking
  • Temporal Masking
  • Auditory Models
• Lecture 6: Quality Measurement of Perceptual Audio Codecs
  • MOS
  • MUSHRA
• Lecture 7: Audio Coding Standards
  • Audio MPEG-1, MPEG-2 y MPEG-2 AAC, MPEG-4.
  • Audio Dolby AC-3.
• Lecture 8: Speech Coding
  • Predictive Coding
  • MLP
  • CELP

Seminars: 8 sessions, 1 hour each.

• Seminar 1: Matlab Review
• Seminar 2: Quantization Entropy Coding
• Seminar 3: Entropy Coding
• Seminar 4: Time Frequency Analysis
• Seminar 5: Partial Exam. 
• Seminar 6: Psychoacoustic Models and Bit allocation
• Seminar 7: Quality Measurements of Perceptual Audio Codecs.
• Seminar 8: Speech Coding.

Labs: 5 sessions, 2 hours each.

• Lab 1: Quantization and Entropy Coding.
• Lab 2: Filterbanks and Perfect Reconstruction.
• Lab 3: Transform coder.
• Lab 4: Psychoacoustic Models for Audio Coding.
• Lab 5: Speech Coding.

 

Resources

Main references

Marina Bosi and Richard E. Goldberg. Introduction to digital audio coding standards, The Springer International Series in Engineering and Computer Science, Vol. 721, 2003. http://www.springer.com/engineering/signals/book/978-1-4020-7357-1

John Watkinson, The MPEG Handbook, Taylor & Francis 2004, ISBN 978-0-240-80578-8. http://www.sciencedirect.com/science/book/9780240805788

  

Complementary references

Udo Zölzer. Digital Audio Signal Processing, Wiley http://eu.wiley.com/WileyCDA/WileyTitle/productCd-0470997850.html

Andreas Spanias, Ted Painter, Venkatraman Atti et al. Audio Signal Processing and Coding, Wiley, 2007. http://eu.wiley.com/WileyCDA/WileyTitle/productCd-0471791474.html ISBN: 978-0-471-79147-8

Atti, V., Spanias, A. On-line simulation modules for teaching speech and audio compression techniques, Frontiers in Education, 2003. FIE 2003. 33rd Annual, T4E - 17-22 Vol.1 , http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?reload=true&arnumber=1263383

Khalid Sayood, Introduction to Data Compression, Elsevier, 2005. http://www.elsevier.com/wps/find/bookdescription.cws_home/706873/description#description John Watkinson, The Art of Digital Audio, Elsevier, 2000. http://www.elsevier.com/wps/find/bookdescription.cws_home/679497/description#description

Kenn Pohlmann, Principles of Digital Audio, McGraw Hill, 2010. http://www.mhprofessional.com/product.php?isbn=0071663460

Teaching material

• Slides and notes.

• Seminar activities.

• Lab instructions.

 

Software

• Octave http://www.gnu.org/software/octave/

• MATLAB