Voice over internet protocol application programming interface for mobile devices

Date of Publication


Document Type

Bachelor's Thesis

Degree Name

Bachelor of Science in Computer Science

Subject Categories

Computer Sciences


College of Computer Studies


Computer Science


Telecommunication is one of the most widely used communication means. In place of the traditional Public Switch Telephone Network (PSTN), a telecommunication which comes with toll fee charges for long distance calls, Internet Protocol (IP) telephony is now used, which comes with lower cost, if not free, for long distance calls. Voice over Internet Protocol (VoIP) is currently present in computers, and PDAs using PocketPC as well. With such technology, these devices can do voice communication with other people from the different parts of the world, with just the use of the internet. However, other mobile devices do not have VoIP yet. In connection with this, an Application Programming Interface (API) for these devices, that would enable further development of VoIP applications, or any other voice enabled applications, is necessary. The proponents created such API for mobile devices, specifically Palm. The API acquires, encodes, compresses, transmits, decompresses, decodes, and plays back voice. The approach devised for the creation of the API consisted the use of the sound streaming through the use of sound call back functions for audio acquisition and encoding, as well as decoding and audio playback Interactive Multimedia Association – Adaptive Differential Pulse Code Modulation (IMA-ADPCM) codec for audio compression and decompression and socket programming, specifically User Datagram Protocol (UDP) through Palm OS’ network library for voice transmission. Tests were conducted to determine the performance of the API through the creation of a sample VoIP application. Test results showed that the API produces an application with a good voice quality of 10.66% margin of error in Diagnostic Rhyme Test (DRT), a 4.4 in the Mean Opinion Score (MOS) Test, and a 0.47-second time delay, compared to the 1.0 MOS and 2.54-second time delay of an existing application, WiFiTalkie. Tests also showed that the API can handle full duplex, half duplex and simplex with a clear voice transmission. Further testing was do

Abstract Format






Accession Number


Shelf Location

Archives, The Learning Commons, 12F, Henry Sy Sr. Hall


Voice computing; Application program interfaces (Computer software)

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