Systems and methods for encoding an audio signal
AssigneeNokia Corporation
InventorJuha Ojanpera
Life of this patent
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Abstract
Methods, computer code products, devices, modules, systems, and encoders are disclosed which are configured to use an adaptive lag search window for determining a lag estimate for a current frame of information in an audio encoding system. The system can determine if the lag estimate is reliable and if not a new search window can be selected and a new lag estimate can be calculated based on the new search window. An adaptive threshold can be compared to the cross correlation for a lag estimate in order to determine whether the lag estimate is reliable. The system can also determine if an encoding gain is likely to be achieved using the prediction and if not, the computationally expensive time-to-frequency transformation can be avoided.
Claims30
A method for determining pitch lag for a current frame of information in an LTP encoding system, the method comprising:
- selecting a lag search window in the current frame in a vicinity of a window, in which previous frame lag was calculated, the lag search window having an upper boundary and a lower boundary;
- and
- calculating a pitch lag estimate in the lag search window for the current frame.
A computer code product for determining pitch lag for a current frame of information in an LTP encoding system, the computer code product comprising:
- computer code configured for:
- selecting a lag search window in the current frame in a vicinity of a window, in which previous frame lag was calculated, the lag search window having an upper boundary and a lower boundary;
- and
- calculating a pitch lag estimate in the lag search window for the current frame.
An device for determining pitch lag for a current frame of information in an LTP encoding system, the encoder comprising:
- a processor;
- memory;
- and
- an encoder configured for:
- selecting a lag search window in the current frame in a vicinity of a window, in which previous frame lag was calculated, the lag search window having an upper boundary and a lower boundary;
- and
- calculating a pitch lag estimate in the lag search window for the current frame.
A module configured for determining pitch lag for a current frame of information in an LTP encoding system, the module comprising:
- an encoder configured to select a lag search window in the current frame in a vicinity of a window, in which previous frame lag was calculated, the lag search window having an upper boundary and a lower boundary;
- and
- an encoder configured to calculate a pitch lag estimate in the lag search window for the current frame.
An audio encoding system for encoding an audio signal, the system comprising:
- an encoder configured to:
- determine pitch lag for a current frame of information in an LTP encoding system by selecting a lag search window in a current frame of audio information in a vicinity of a window, in which previous frame lag was calculated, the lag search window having an upper boundary and a lower boundary;
- and
- calculating a pitch lag estimate in the lag search window for the current frame.
The audio encoding system of claim 27, wherein selecting a new lag search further comprises:
- setting a lower search window corresponding to an area from a beginning of the current frame to the lower boundary;
- setting an upper search window corresponding to an area from the upper boundary to an end of the current frame;
- calculating a lower pitch lag for in the lower search window and an upper pitch lag in the upper window;
- selecting a new search window locator corresponding to the one of either the lower pitch lag or upper pitch lag that produces a maximum cross correlation;
- setting a new search window around the new search window locator;
- calculating a new pitch lag for the new search window;
- and
- selecting as a lag estimator the one of either the pitch lag or the new pitch lag that produces a maximum cross correlation.
Dependencies are inferred from the claim text.