Coverage
The diphone inventory determines which words can be synthesized successfully.
Diphone Inventory
Core transition units, safe filenames, coverage strategy, and practical TTS resources
Dataset
Diphone Inventory
This page documents the practical diphone inventory used in the Bishnupriya Manipuri TTS workflow, including diphone structure, safe filename mapping, inventory layers, recording priorities, and validator-facing organization.
About this dataset page.
The article series explains the theory of diphone-based synthesis.
This page is the working resource layer: a practical reference for organizing,
recording, naming, validating, and expanding the diphone inventory.
1. What Is a Diphone?
A diphone is the transition between two adjacent phonemes. In a diphone-based TTS system, words are synthesized by joining the audio files corresponding to these transitions.
Word ↓ IPA ↓ Phoneme sequence ↓ Diphone sequence ↓ Safe filenames ↓ Audio playback
Example:
Word: কথা
IPA: kɔtʰa
Phonemes: k ɔ tʰ a
Diphones:
Word: কথা
IPA: kɔtʰa
Phonemes: k ɔ tʰ a
Diphones:
#-k
k-ɔ
ɔ-tʰ
tʰ-a
a-#
2. Why the Inventory Matters
Consistency
A stable inventory ensures that dictionary pages, validators, and TTS playback all expect the same filenames and transitions.
Efficiency
A well-designed inventory avoids recording unnecessary combinations while still covering the language effectively.
3. Structural Types of Diphones
| Type | Example | Purpose |
|---|---|---|
| Boundary → phoneme | #-k | Word-initial entry into speech |
| Phoneme → boundary | a-# | Word-final exit from speech |
| Consonant → vowel | k-a | Very common transition type |
| Vowel → consonant | a-r | Common syllable-closing transition |
| Consonant → consonant | g-n | Needed for clusters and learned forms |
| Vowel → vowel | a-i | Needed in vowel sequences and transitions |
4. Safe Filename Mapping
Raw IPA symbols are not ideal for filesystem storage and URL loading. Therefore, each diphone is converted to a stable safe filename form.
| IPA Symbol | Safe Form | Example |
|---|---|---|
| # | sil | #-d → sil-d.wav |
| aː | aa | ʃ-aː → sh-aa.wav |
| iː | ii | d-iː → d-ii.wav |
| uː | uu | k-uː → k-uu.wav |
| ʃ | sh | i-ʃ → i-sh.wav |
| ŋ | ng | a-ŋ → a-ng.wav |
| ɔ | aw | k-ɔ → k-aw.wav |
| ə | schwa | k-ə → k-schwa.wav |
Safe filename rules should be frozen before rebuilding the diphone folder.
If the naming rules change mid-project, old files become incompatible with new TTS expectations.
5. Inventory Layers
Core Inventory
The smallest practical set for broad TTS usefulness.
- word-initial boundary diphones
- word-final boundary diphones
- common consonant-vowel transitions
- common vowel-consonant transitions
Target size: about 180–220 diphones
Extended Inventory
Additional transitions for broader lexical coverage.
- rare clusters
- learned Sanskritic forms
- less frequent consonant transitions
- special vowel transitions
Target size: about 250–320 diphones
6. Example Core Inventory Table
| Diphone | Safe Filename | Priority | Example Word |
|---|---|---|---|
| #-k | sil-k.wav | Core | কর |
| k-ɔ | k-aw.wav | Core | কথা |
| ɔ-tʰ | aw-th.wav | Core | কথা |
| tʰ-a | th-a.wav | Core | কথা |
| a-# | a-sil.wav | Core | কথা |
| #-d | sil-d.wav | Core | দিশা |
| d-i | d-i.wav | Core | দিশা |
| i-ʃ | i-sh.wav | Core | দিশা |
| ʃ-a | sh-a.wav | Core | দিশা |
| a-r | a-r.wav | Core | উপকার |
7. Example Extended Inventory Table
| Diphone | Safe Filename | Priority | Example Word |
|---|---|---|---|
| g-n | g-n.wav | Extended | অগ্নি |
| k-ʃ | k-sh.wav | Extended | অক্ষর |
| ʃ-ɔ | sh-aw.wav | Extended | অক্ষর |
| i-tʃ | i-ch.wav | Extended | ইচ্ছা |
| tʃ-i | ch-i.wav | Extended | ইচ্ছা |
| ɔ-r | aw-r.wav | Extended | অক্ষর |
8. Recording Priority Strategy
Not all diphones should be recorded at the same time. A practical recording plan should start with the most useful transitions.
Priority 1
High-frequency boundary, consonant-vowel, and vowel-consonant diphones.
Priority 2
Common lexical cluster transitions and high-value extended diphones.
Priority 3
Rare learned forms, less frequent clusters, and low-coverage diphones.
9. Validator-Facing Organization
The inventory should not only exist as a concept. It should be organized in a way that supports practical validation.
Useful validator-facing fields:
- diphone
- safe filename
- priority level
- recorded status
- segmented status
- uploaded status
- validator pass/fail
- example source word
10. Rebuild Principles
Freeze IPA Rules
Rebuild only after pronunciation logic is stable.
Freeze Safe Filenames
Do not rename mapping conventions in the middle of the rebuild.
Use a Clean Folder
Rebuild in a fresh diphone directory to avoid mixing old and new files.
11. Related Archive Pages
Article 5
Read the research chapter on diphone inventory design.
IPA Toolkit
Review pronunciation rules and conversion logic.
Resources
Return to the broader dataset/resources overview.
Inventory note.
This page should gradually evolve from a conceptual inventory page
into a live working dataset page, including actual downloadable tables,
coverage trackers, and validator-facing spreadsheets.