The current invention discloses methods, applications, and devices for audio transmission from a mobile terminal. After receiving an audio signal transmission request from a user, the mobile terminal may initiate a recording session to record audio signals into audio frames. During the recording session, the terminal may adjust the audio codecs used for encoding the audio frames based on the workload and the performance of the terminal. By measuring and evaluating the encoding time, the terminal may change between using a floating-point AMR audio codec and a fixed-point AMR audio codec. The encoded audio frames are transmitted to a remote server. The current invention provides a flexible and efficient approach for audio signal encoding and transmission, balancing signal integrity and encoding speed at the same time.