General Notes

Sanskrit/Pali in East Asian Scripts

Most of the East Asian scripts are derived from the Pallava Grantha Script, a Brahmic offshoot again. Hence they retain all the features of the Brahmi Script such as the Alpha-Syllabic Structure of the Script, Complex Conjuncts, Inherent vowel sound, Virama etc.  However over the years, the pronunciation of the consonants have completely deviated from the mainland Indic model, and the script has been completely nativized for suit the local phonetics. Some scripts also developed additional vowel signs and consonantal signs too.

However when the scripts are employed to write Sanskrit/Pali, the archaic Indic systems is still retained and the text is read according to Indian conventions.Ideally speaking, to read Sanskrit/Pali in these scripts one has to depart from the Traditional native reading rules and apply the Sanskrit/Pali [Indic] reading rules to the Script. But some times the East Asian natives also tend to apply some of their own native phonetics when reading Sanskrit/Pali texts.

[A parallel situation in Indic Script would be Devanagari. When written Devanagari is read as "Hindi", the reading rules of Hindi is applied, however when the same text is read as Sanskrit, the reading rules of Sanskrit is applied. e.g The devanagari text विश्वविद्यालय would be a pronounced as VishvVidyaalay when read as Hindi, but when the text is read as Sanskrit, it will be pronounced VishvaVidyaalaya ]

http://www.pali.pratyeka.org/#Phonology has a good coverage on the pronunciation of Pali among East Asians.

Do note the Converter only supports the Character (sub)set that is used for writing Sanskrit/Pali. 

Diacritic Characters

Characters present is some scripts are absent in the other scripts. For Instance, the North Indic Scripts have letters to denote the perso-arabic characters in their Script, which the South Indic scripts lack. Similarly the South Indic scripts have short e/o which the North Indic scripts lack. Also some scripts like Sinhala, have specific native consonants like the Prenasalized consonants. To normalize the entire Script range diacritics like Apostrophe, Carets, Dots etc has been used to represent the characters that are present in one script but lacking in others. Through this it is possible to accurately represent the source Script in the Target script, thus enabling reversible lossless round-trip transliteration.

The Diacritic Characters are enabled only if "Preserve source" is selected.

கொல் (Tamil) - કો˘લ્ (Gujarati)

ఎప్పుడు (Telugu) - ଏ˘ପ୍ପୁଡୁ (Oriya)

हॉकी (Devanagari) - ಹಾʼಕೀ (Kannada)

The diacritics have been employed only for Indian Scripts. For East Asian Scripts, the approximate equivalent character is used instead.

Nukta Characters

Nukta is a dot like characters present in some Indic scripts which can be used to extended the alphabets to represent non-native phonemes. The North Indic languages use the Nukta to represent perso-arabic sounds. 

With respect to the converter, for those language having Nukta, the new characters has been extended by using Nukta. For Instance, The equivalent for Tamil ன in North Indic languages has been created by placing Nukta on na such as ન઼, ନ଼, ন় etc. For, Scripts without Nukta, · has been used to a diacritic for Nukta. 

Specifically for Tamil, ஃ acts like a de-facto Nukta. [The letter natively represents a 'h' like sound - Voiceless Velar Fricative]. In Modern Tamil, it  is  used akin to a Nukta, e.g It is used to represent sounds like fa - ஃப & za - ஃஜ by modifying the consonant it follows. This usage has been extended in the converter to express the whole perso-arabic character range of the North Indic Scripts.

View Character Matrix for the Complete Mapping of Scripts.

Fonts

Indian Scripts

Windows from the XP edition comes with default fonts for all Indian languages (except Oriya). Starting from Windows Vista, it comes with fonts with Oriya too with support for the latest Unicode version. Characters which were added later like South Indic Avagrahas, Malayalam Chillus, Kananda Nukta, Bengali Khanda Ta, Tamil SHA are not supported in the default Indic fonts for XP. In that case, install the fonts of Indolipi package, they have support for all these characters. The typeface of the Indolipi fonts are also much better than these default fonts.

If not on Windows, there are scores of opensource Indic fonts, which must not be hard find out !

Sinhala & East Asian Scripts

Windows 7 has default fonts for Tibetan, Khmer & Sinhala. For Burmese, check the Burmese page for more information on the Burmese fonts. 

Check the below links for information on fonts for Various Scripts:

http://salrc.uchicago.edu/resources/fonts/

http://www.wazu.jp/

Windows XP  - Uniscribe Issues

The default Uniscribe Engine of Windows XP doesn't not support the text rendering of Sinhala & Tibetan (I suppose its the same case with other East asian scripts as well). he Uniscribe.dll must be updated to the latest version for displaying these scripts in Windows XP. Sinhala kit updates the Uniscribe.dll file (and installs a couple of Sinhala fonts & keyboard drivers as well). Its suffice for others to just upgrade the Unscribe.dll without going into Sinhala related specifics.

References & Further Reading

1. The Unicode Standard - Chapter 9 - South Asian Scripts - I

2. The Unicode Standard - Chapter 10 - South Asian Scripts - II

3. The Unicode Standard - Chapter 11 - South-East Asian Scripts

4. ISCII Standard

5. Cambridge University Library - Transliteration Tables : South Asian Scripts 

6. Pali Pratyeka - Pali Rosetta Stone

7. Indolipi Package

Acknowledgements

Dr. Naa Ganesan (though we have a plethora of opinion differences), who initially prompted me into doing this, and provided much needed initial support & feedback. Vedic Scholar Shriramana, for asking me add the east asian Scripts & his support. Dr. Jean-Luc Chevillard for his support & for clarifying my queries with his peers.