1. A Text-to-Speech Synthesis System
Presented By:
Michael Beddaoui
Abdel-Aziz El-Solh

2. Presentation Outline Introduction Background
3 Components of TTS System
Text Pre-processing Aziz
Prosody Mike
Concatenation Mike
Summary
What has been done / Future Work
Conclusion
Questions

3. What is a TTS System? Definition:
A system which takes as input a sequence of words and converts them to speech
Applications:
Services for the hearing impaired
Reading aloud
Commercial TTS Systems:
Festival
Bell Labs TTS

4. Different TTS Systems Phoneme-Based TTS System Phonemes are:
The minimal distinctive phonetic units
Relatively small in number (39 phonemes in English)
Disadvantage:
Phonemes ignore transitional sound !!!

5. Different TTS Systems (cont’d)
Diphone-Based TTS System
Diphones are:
Made up of 2 phonemes
Incorporate transitional sound
Make for better sounding speech
Disadvantage:
Over 1500 diphones in the English language !!!

6. Fundamental Components
TTS System
words
Text
Pre-processing
Prosody
Concatenation

7. Text Pre-Processing Input Output Objective
String of characters (sentence)
Output
String of diphone symbols
Objective
Perform sentence level analysis
Punctuation marks
Pauses between words
Convert all input to corresponding diphones

8. Text Pre-Processing (Block Diagram)
Number Converter
Number Converter
Acronym
Converter
Word
Segmenter
Word to
Diphone
Translator
(Phonetization)
MLDS
Diphone
Dictionary

9. Number Converter Replace numerals with their textual versions
one hundred
Handle fractional and decimal numbers
point two five

10. Text Pre-Processing (Block Diagram)
Number Converter
Acronym
Converter
Acronym
Converter
Word
Segmenter
Word to
Diphone
Translator
(Phonetization)
MLDS
Diphone
Dictionary

11. Acronym Converter Replace acronyms with single letter components
A.B.C A B C
Change abbreviations to full textual format
Mr Mister

12. Text Pre-Processing (Block Diagram)
Number Converter
Acronym
Converter
Word
Segmenter
Word
Segmenter
Word to
Diphone
Translator
(Phonetization)
MLDS
Diphone
Dictionary

13. Word Segmenter Divide sentence into word segments Segments can be:
Special delimiter to separate segments (i.e. ‘||’)
Segments can be:
A single word
An acronym
A numeral
Identify punctuation marks

14. Text Pre-Processing (Block Diagram)
Number Converter
Acronym
Converter
Word
Segmenter
Word to
Diphone
Translator
(Phonetization)
Word to
Diphone
Translator
(Phonetization)
MLDS
Diphone
Dictionary

15. Word To Diphone Converter (Phonetization)
Purpose
Translate words to their diphone representations
Resource
Dictionary of words and their diphones (derived from CMU phoneme database)
Over 175,000 words supported

16. start index, end index, middle index
W-to-D Converter Cont’d
Implementation
Binary Search Algorithm in C
Start with whole dictionary as search range
start index, end index, middle index
If target word alphabetically less then middle word,
then ignore second half (i.e. end index = middle index)
else ignore first half (i.e. start index = middle index)
Repeat until word found or range contains zero words

17. W-to-D Converter Cont’d
Advantages
Fast search times
Search range decreases exponentially with each iteration (max of 1 sec currently)
Less complicated to implement
Compared to indexing dictionary or
Importing the dictionary to an internal structure

18. Text Pre-Processing (Block Diagram)
Number Converter
Acronym
Converter
Word
Segmenter
Word to
Diphone
Translator
(Phonetization)
MLDS
MLDS
Diphone
Dictionary

19. The Multi-Level Data Structure
Contains all necessary data for the next sub-system:
Word
Diphone representation
Prosodic parameters for each diphone
This reflects both word-level and sentence- level prosody
Allows for modularization

20. Prosody done Diphone Acoustic MLDS Concatenation Retrieval
Manipulation
Diphone
Retrieval
Concatenation
yes no
Diphone
Database

21. Diphone Retrieval Database of recorded diphones
Every diphone matched with txt file
Distinguished by type (CC, CV, VC, VV)
References to specific components within waveform
Store diphone waveform and prosodic parameters in variables

22. Properties of Speech Signals
eg. cat.wav c a t
Non-
Periodic
Periodic
Non-
Periodic

23. Acoustic Manipulation - MATLab
Recognizes wave files (.WAV)
load, play, write
Vast array of signal processing tools
Built-in functions
Ease of debugging
GUI-capable

24. Pitch/Duration/Amplitude Alteration
Pitch – vowels only
As pitch increases, pitch period shrinks
As pitch decreases, pitch period expands
Need to alter length between pitch marks in order to alter pitch of speech signal

25. Altering Pitch = X Original diphone Extracted pitch period Hanning
window
Hanned
pitch period
‘C_A’

26. Altering Pitch Cont’d PSOLA – Pitch Synchronous Overlap and Add =
50% Overlap + Add
Pitch Up > 50%
Pitch Down < 50%

27. Altering Pitch Cont’d = X Kaiser window X 12 -naturally spoken
vowels contain 12-18
pitch marks =

28. Altering Duration Altering Amplitude
Increase number of PSOLA iterations (overlaps) to increase duration
Decrease number of PSOLA iterations (overlaps) to decrease duration
Altering Amplitude
Multiplying the signal by a constant
If constant > 1, amplitude increase
If constant < 1, amplitude decrease

29. Concatenation
Diphones
Words
Using PSOLA at the joining ends
Ensures smooth transition
Words
Sentence
Straight joining at the end points due to presence of pauses

30. Summary TTS System System modularized words Text Pre-processing
Prosody
Concatenation
System modularized

31. Progress Work Completed / Current Status Work To Be Done
Text pre-processing and prosodic manipulation for a multi-syllable word
Diphone concatenation
200+ diphones in database
Fully functional GUI implemented
Work To Be Done
Sentence level synthesis
Expand diphone database
Fine-tuning and enhancing
Prepare for Poster Fair
Write final report

32. Questions?
Contact Information
Michael Beddaoui
Abdel-Aziz El-Solh