Audio signal reproducing apparatus
View Patent ↗A small-sized audio signal reproducing apparatus for hearing reproduced audio signals with the aid of a headphone is disclosed. Digitized and compression encoded audio signals, stored in a semiconductor memory, are read out so as to undergo a decoding operation, which is an inverse operation to compression encoding, to reproduce the audio signals, and the reproduced signals are heard by the headphone. The apparatus may be significantly reduced in size and weight as compared to the apparatus in which a tape or a disk is used as the recording medium.
1. A compact audio signal reproducing apparatus comprising
a memory unit for storing digitized and high-efficiency compression encoded audio data;
a decoder for reading out data stored in said memory unit and decoding the read-out data by performing an inversion of the compression encoding;
a digital/analog converter for converting output signals from said decoder into analog signals;
a headphone unit for said analog signals from said digital analog converter and converting said analog signals from said digital/analog converter into acoustic signals; and
a housing for containing said memory unit, said decoder, and said digital/analog converter, said housing being compact,
wherein said audio data is compression encoded by sub-band dividing audio data by dividing said audio data into a plurality of frequency bands, and
quantizing a frequency component transformed from audio data for each of said plurality of frequency bands according to a masking spectrum associated with said frequency component for each of said plurality of frequency bands and a minimum audible curve based on the human auditory sense.
2. The compact audio signal reproducing apparatus according to claim 1 wherein said audio data is compression encoded by allowable noise level setting based on said masking spectrum and said minimum audible curve for each of said plurality of frequency bands and
quantizing said frequency component by the number of bits allocated in accordance with the level of a difference between said frequency component and said allowable noise level.
3. The compact audio signal reproducing apparatus according to claim 1 , further comprising a rate controller for controlling a bit rate of said compression encoded audio data by increasing or decreasing said allocated number of bits associated with said frequency component.
4. A portable audio player comprising:
a memory unit configured to store digitized high-efficiency encoded audio data;
a decoder configured to read out data stored in said memory unit and to decode the read-out data by performing an inversion of a compression encoding used to obtain the high-efficiency encoded audio data;
a digital/analog converter configured to convert output signals from said decoder into analog signals for a transmission to a headphone; and
a portable housing containing said memory unit, said decoder, and said digital/analog converter,
wherein said audio data is compression encoded by
sub-band dividing audio data by dividing the audio data into a plurality of frequency bands, and
quantizing a frequency component transformed from audio data for each of the plurality of frequency bands according to a masking spectrum associated with the frequency component for each of the plurality of frequency band and a minimum audible curve based on human auditory sense.