Adaptive gain-shape rate sharing
An object of embodiments of the present invention is to provide an improved gain-shape VQ. This is achieved by determining a number of bits to be allocated to a gain adjustment- and shape-quantizer for a plurality of combinations of a current bit rate and a first signal property. The determined allocated number of bits to the gain adjustment- and shape quantizer should provide a better result for the given bitrate and signal property than using a single fixed allocation scheme. That can be achieved by deriving the bit allocation by using an average of optimal bit allocations for a training data set. Thus by pre-calculating a number of bits to the gain adjustment and the shape quantizers for a plurality of combinations of the bit rate and a first signal property and creating a table indicating the number of bits to be allocated to the gain adjustment- and the shape-quantizers for a plurality of combinations of the bit rate and a first signal property. In this way, the table can be used for achieving an improved bit allocation.
1. A method in a digital encoder for encoding an audio signal, the method comprising:
receiving the audio signal;
determining a current bitrate and a value for a first signal property, the first signal property being a bandwidth of the audio signal or a length of the audio signal;
identifying a bit allocation for a gain adjustment quantizer and a shape quantizer to be used for digitally encoding a gain shape vector for the received audio signal, based on the determined current bitrate and the value for the first signal property, by using information from a table indicating a number of bits to be allocated to the gain adjustment quantizer and the shape quantizer for each of a plurality of combinations of determined current bitrate and values for the first signal property; and
digitally encoding the gain shape vector for the received audio signal, using the identified bit allocation.
2. The method of claim 1 , wherein the first signal property is bandwidth.
3. The method of claim 2 , wherein the bandwidth is fixed and known at the encoder.
4. The method of claim 1 , wherein the first signal property is signal length.
5. The method of claim 1 , wherein the encoder is a transform domain audio encoder.
6. A method in a digital decoder for decoding a digitally encoded audio signal, the method comprising:
receiving the digitally encoded audio signal;
determining a current bitrate and a value for a first signal property, the first signal property being a bandwidth of the audio signal or a length of the audio signal;
identifying a bit allocation for a gain adjustment dequantizer and a shape dequantizer to be used for decoding a gain shape vector from the digitally encoded audio signal, based on for the determined current bitrate and the value for the first signal property, by using information from a table indicating a number of bits to be allocated to the gain adjustment dequantizer and the shape dequantizer for each of a plurality of combinations of determined current bitrate and values for the first signal property; and
decoding the gain shape vector from the digitally encoded audio signal, using the identified bit allocation.
7. The method of claim 6 , wherein the first signal property is bandwidth.
8. The method of claim 7 , wherein the bandwidth is fixed and known at the encoder.
9. The method of claim 6 , wherein the first signal property is signal length.
10. The method of claim 6 , wherein the decoder is a transform domain audio decoder.
11. An encoder apparatus for digitally encoding an audio signal, the encoder comprising:
a gain adjustment quantizer and a shape quantizer; and
an adaptive bit sharing circuit configured to determine a current bitrate and a value for a first signal property, to identify a bit allocation for the gain adjustment quantizer and the shape quantizer for the determined current bitrate and the value for the first signal property by using information from a table indicating a number of bits to be allocated to the gain adjustment quantizer and the shape quantizer for each of a plurality of combinations of determined current bitrate and values for the first signal property, the first signal property being a bandwidth of the audio signal or a length of the audio signal;
wherein the gain adjustment quantizer and shape quantizer are configured to apply the identified bit allocation when digitally encoding the gain shape vector.
12. The encoder apparatus of claim 11 , wherein the first signal property is bandwidth.
13. The encoder apparatus of claim 12 , wherein the bandwidth is fixed and known at the encoder.
14. The encoder apparatus of claim 11 , wherein the first signal property is signal length.
15. The encoder apparatus of claim 11 , wherein the encoder is a transform domain audio encoder.
16. A decoder apparatus for decoding a gain shape vector for a digitally encoded audio signal, the decoder apparatus comprising:
a gain adjustment dequantizer and a shape dequantizer; and
an adaptive bit sharing circuit configured to determine a current bitrate and a value for a first signal property value, to use information from a table indicating a number of bits to be allocated to the gain adjustment dequantizer and the shape dequantizer for each of a plurality of combinations of determined current bitrate and values for the first signal property, and to identify, using said table, a bit allocation for the gain adjustment dequantizer and the shape dequantizer for the determined current bitrate and the value for the first signal property, the first signal property being a bandwidth of the audio signal or a length of the audio signal;
wherein the gain adjustment dequantizer and shape dequantizer are configured to apply the identified bit allocation when decoding the gain shape vector from the digitally encoded audio signal.
17. The decoder apparatus of claim 16 , wherein the first signal property is bandwidth.
18. The decoder apparatus of claim 17 , wherein the bandwidth is fixed and known at the encoder.
19. The decoder apparatus of claim 16 , wherein the first signal property is signal length.
20. The decoder apparatus of claim 16 , wherein the decoder is a transform domain audio decoder.
21. A mobile device comprising an encoder apparatus for digitally encoding an audio signal, the encoder apparatus comprising:
a gain adjustment quantizer and a shape quantizer; and
an adaptive bit sharing circuit configured to determine a current bitrate and a value for a first signal property value, to identify a bit allocation for the gain adjustment quantizer and the shape quantizer for the determined current bitrate and the value for the first signal property by using information from a table indicating a number of bits to be allocated to the gain adjustment quantizer and the shape quantizer for each of a plurality of combinations of determined currennt bitrate and values for the first signal property, the first signal property being a bandwidth of the audio signal or a length of the audio signal;
wherein the gain adjustment quantizer and shape quantizer are configured to apply the identified bit allocation when digitally encoding the gain shape vector.
22. A mobile device comprising a decoder apparatus for decoding a gain shape vector for a digitally encoded audio signal, the decoder apparatus comprising:
a gain adjustment dequantizer and a shape dequantizer; and
an adaptive bit sharing circuit configured to determine a current bitrate and a value for a first signal property value, to use information from a table indicating a number of bits allocated to the gain adjustment dequantizer and the shape dequantizer for each of a plurality of combinations of determined current bitrate and values for the first signal property, and to identify, using said table, a bit allocation for the gain adjustment dequantizer and the shape dequantizer for the determined current bitrate and the value for the first signal property, the first signal property being a bandwidth of the audio signal or a length of the audio signal;
wherein the gain adjustment dequantizer and shape dequantizer are configured to apply the identified bit allocation when decoding the gain shape vector from the digitally encoded audio signal.