Apparatus and method for post-processing and outputting digital audio data in real time

Abstract

A digital audio data output device having first and second post-processors configured to process received digital audio data in parallel. Each processor includes a mixer unit configured to process received digital audio data on the fly in response to a channel mode control signal, and a volume control unit configured to adjust volume level of output of the mixer unit on the fly in response to a volume level control signal. Where the digital audio data corresponds to two channel data, each mixer unit includes first and second buffers configured to respectively store the first and second channel data in the two channel data, a calculator configured to calculate mix data from the outputs of the first and second buffers, a third buffer configured to store the mix data, and an output unit. The output unit is configured to select and output one of the received digital audio data, the output of the first buffer, the output of the second buffer, the mix data, and output of the third buffer, as the output of the mixer unit.

1 . A post-processor for processing received digital audio data, comprising:
 a mixer unit configured to process the digital audio data in response to a channel mode control signal; and   a volume control unit configured to adjust the volume level of the output of the mixer unit in response to a volume level control signal.   
   
   
       2 . The post-processor of  claim 1 , wherein the received digital audio data correspond to PCM data. 
   
   
       3 . The post-processor of  claim 1 , wherein the received digital audio data correspond to two channel data. 
   
   
       4 . The post-processor of  claim 3 , wherein the mixer unit includes a multiplexer, and wherein the multiplexer selects one of stereo data, single right channel data, single left channel data and mix data, as the output of the mixer unit. 
   
   
       5 . The post-processor of  claim 3 , wherein the mixer unit includes:
 a first buffer configured to store the first channel data in the two channel data;   a second buffer configured to store the second channel data in the two channel data;   a calculator configured to calculate mix data based on the output of the first buffer and the output of the second buffer;   an output unit configured to select and output one of the received digital audio data, the output of the first buffer, the output of the second buffer, the mix data.   
   
   
       6 . The post-processor of  claim 5 , wherein the mixer unit further includes:
 a third buffer configured to store the mix data; and wherein the output unit is configured to select and output one of the received digital audio data, the output of the first buffer, the output of the second buffer, the mix data, and the output of the third buffer.   
   
   
       7 . The post-processor of  claim 6 , wherein the first buffer stores a sample of the received digital audio data in synchronization with a clock signal, the second buffer stores the output of the first buffer in synchronization with the clock signal, and the third buffer stores the mix data in synchronization with the clock signal. 
   
   
       8 . The post-processor of  claim 1 , wherein the volume control unit gradually adjusts the current volume level of the output of the mixer unit to a target volume level that is dynamically determined in response to the volume level control signal. 
   
   
       9 . The post-processor of  claim 1 , wherein the volume control unit includes:
 a current volume register configured to store the current volume level;   a target volume register configured to store the target volume level;   a current volume level update unit configured to increment or decrement the current volume level by predetermined increments of volume until the current volume level corresponds to the target volume level; and   a scaler configured to scale the output of the mixer unit according to the current volume level.   
   
   
       10 . The post-processor of  claim 1 , wherein the volume control unit includes a scaler including a sequential multiplier configured to multiply the output of the mixer unit by the current volume level. 
   
   
       11 . The post-processor of  claim 10 , wherein the scaler includes:
 an adder configured to perform an addition operation upon first input data and second input data of the adder in synchronization with a bit clock;   a register configured to store the output of the adder in synchronization with the bit clock;   a shifter configured to perform 1-bit right shift of the output of the adder in synchronization with the bit clock; and   a control unit configured to control a selection of the first input of the adder and a selection of the second input of the adder according to each bit of the current volume level from LSB to MSB,   
   
   
       12 . The post-processor of  claim 11 , wherein:
 when the each bit of the current volume level corresponds to ‘1’, the output of the mixer unit is selected as the first input of the adder, and one of the output of the shifter and ‘zero’ is selected as the second input of the adder’; and   when the each bit of the current volume level corresponds to ‘0’, ‘zero’ is selected as the first input of the adder, and one of the output of the shifter and ‘zero’ is selected as the second input of the adder, wherein the control unit selects ‘zero’ instead of the output of the shifter as the second input of the adder before any each bit of the current volume level corresponds to ‘1’, and wherein the control unit selects the output of the shifter as the second input of the adder after any each bit of the current volume level corresponds to ‘1’.   
   
   
       13 . A digital audio data output device comprising:
 first and second processors each configured to process the digital audio data; and   first and second transmitters configured to output the digital audio data processed by first and second processors, respectively, in a predetermined transmission mode.   
   
   
       14 . The digital audio data output device of  claim 13 , further comprising: a memory configured to buffer received digital audio data temporarily; and wherein each of the first and second post-processors is configured to read the received digital audio data from the memory and process the read digital audio data. 
   
   
       15 . The digital audio data output device of  claim 14 , wherein each of the first and second processors includes:
 a mixer unit configured to process the received digital audio data in to response to a channel mode control signal; and   a volume control unit configured to adjust volume level of output of the mixer unit in response to a volume level control signal.   
   
   
       16 . The digital audio data output device of  claim 15 , wherein the digital audio data correspond to PCM data. 
   
   
       17 . The digital audio data output device of  claim 15 , wherein the digital audio data correspond to two channel data, and
 wherein the mixer unit includes:
 a first buffer configured to store the first channel data in the two channel data; 
 a second buffer configured to store the second channel data in the two channel data; 
 a calculator configured to calculate mix data from the output of the first buffer and the output of the second buffer; and 
 an output unit configured to select and output one of the received digital audio data, the output of the first buffer, the output of the second buffer, and the mix data, as the output of the mixer unit. 
   
   
   
       18 . The digital audio data output device of  claim 17 , further comprising a third buffer configured to store the mix data, and wherein the output unit is configured to select and output one of the received digital audio data, the output of the first buffer, the output of the second buffer, the mix data, and output of the third buffer as the output of the mixer unit. 
   
   
       19 . The digital audio data output device of  claim 15 , wherein the volume control unit includes:
 a current volume register configured to store the current volume level;   a target volume register configured to store a target volume level;   a current volume level update unit configured to increment or decrement the current volume level until the current volume level corresponds to the target volume level; and   a scaler configured to scale the output of the mixer unit according to the current volume level.   
   
   
       20 . The digital audio data output device of  claim 15 , wherein the scaler includes a sequential multiplier configured to multiply the output of the mixer unit by the current volume level. 
   
   
       21 . The digital audio data output device of  claim 15 , wherein the volume control unit includes a scaler including:
 an adder configured to perform an addition operation first and second inputs of the adder in synchronization with a bit clock;   a register configured to store the output of the adder in synchronization with the bit clock;   a shifter configured to perform 1-bit right shift of the output of the adder in synchronization with the bit clock; and   a control unit configured to determine the first and second inputs of the adder according to each bit of the current volume level in sequence of LSB to MSB.   
   
   
       22 . The digital audio data output device of  claim 21 , wherein:
 when the each bit of the current volume level corresponds to ‘1’, the output of the mixer unit is selected as the first input of the adder and one of the output of the shifter or ‘zero’ is selected as the second input of the adder; and   when the each bit of the current volume level corresponds to ‘0’, ‘zero’ is selected as the first input of the adder, and one of the output of the shifter or ‘zero’ is selected as the second input of the adder, wherein the control unit selects ‘zero’ as the second input of the adder before any bit of the current volume level corresponds to ‘1’, and the control unit selects the output of the shifter as the second input of the adder while and after any bit of the current volume level corresponds to ‘1’.   
   
   
       23 . A method of outputting received digital audio data, comprising:
 setting a channel mode and a target volume level;   storing the received digital audio data in a memory;   processing the digital audio data according to the channel mode;   adjusting the volume level of the processed digital audio data according to the target volume level; and   outputting the digital audio data having the adjusted volume level in a predetermined transmission mode.   
   
   
       24 . The method of  claim 23 , wherein adjusting the volume level includes:
 comparing the current volume level with the target volume level;   updating the current volume level by incrementing or decrementing the current volume level until the current volume level corresponds to the target volume level; and   scaling the volume level of the digital audio data according to the current volume level.   
   
   
       25 . The method of  claim 24 , wherein scaling the volume level of the digital audio data includes multiplying the processed digital audio data by the current volume level.