The sounds of the chanting are presented by Boutsulin Vihara to the best of knowledge and ability precisely close to the mantra as extracted principally from Mahakaruna Dharani Sutra which was translated in the Tang Dynasty in China by a holiest practitioner Bhagavaddharma from West India in the 7th Century.
Mahakaruna means great compassion, sympathy or loving kindness, also refers to gratification and equanimity.
For detail, please refer to the website: http://mahakaruna.dharma.tw