Classification Between Time-Domain Coding and Frequency Domain Coding

An encoder for processing speech signals prior to encoding a digital signal comprising audio data, the encoder comprising:

• a memory storing computer instructions;
• a processor coupled to retrieve and execute the computer instructions to prompt the processor to perform the steps of:
• selecting frequency domain coding or time domain coding based on a coding bit rate to be used for coding the digital signal;
• and
• detecting a short pitch lag of the digital signal, wherein the detecting the short pitch lag comprises:
• detecting whether the digital signal comprises a short pitch signal for which the pitch lag is shorter than a pitch lag limit, wherein the pitch lag limit is a minimum allowable pitch for a Code Excited Linear Prediction Technique (CELP) algorithm for coding the digital signal, wherein the minimum allowable pitch is 34 when a sampling rate is 12.8 kHz.

A device for processing speech signals prior to encoding a digital signal comprising audio data, the device comprising:

• a central processing unit (CPU), a memory and an encoder implemented by an application specific integrated circuit (ASIC), wherein the encoder is configured to:
• select frequency domain coding or time domain coding based on
• a coding bit rate to be used for coding the digital signal and
• detecting whether the digital signal comprises a short pitch signal for which the pitch lag is shorter than a pitch lag limit, wherein the pitch lag limit is a minimum allowable pitch for a Code Excited Linear Prediction Technique (CELP) algorithm for coding the digital signal, wherein the minimum allowable pitch is 34 when a sampling rate is 12.8 kHz.