Selecting pitch lag

A method for determining a pitch lag for a signal divided into frames, comprising:

• performing a first estimation for a current frame to acquire a first estimate as a lag that maximizes a first correlation function associated to the current frame;
• performing a second estimation for the current frame to acquire a second estimate by searching for a lag which maximizes a second correlation function in a second subinterval which comprises a pitch lag selected for a previous frame, wherein performing the second estimation is acquired on a basis of a result of selecting performed at the previous frame;
• and
• selecting between the first estimate acquired at the first estimation and the second estimate acquired at the second estimation on a basis of a first and a second normalized autocorrelation measurements,
• wherein the selecting comprises performing a comparison between:
• a downscaled version of the first normalized autocorrelation measurement, associated to the current frame and acquired at a lag corresponding to the first estimate;
• the second normalized autocorrelation measurement, associated to the current frame and acquired at a lag corresponding to the second estimate;
• and
• selecting the first estimate when the second normalized autocorrelation measurement is less than the downscaled version of the first normalized autocorrelation measurement, and/or selecting the second estimate when the second normalized autocorrelation measurement is greater than the downscaled version of the first normalized autocorrelation measurement,
• wherein the method further comprises using the selected lag for long-term post filtering (LTPF).

A method for encoding a bitstream for a signal divided into frames, comprising:

• performing a first estimation for a current frame to acquire a first estimate as a lag that maximizes a first correlation function associated to the current frame;
• performing a second estimation for the current frame to acquire a second estimate by searching for a lag which maximizes a second correlation function in a second subinterval which comprises a pitch lag selected for a previous frame, wherein performing the second estimation is acquired on a basis of a result of selecting performed at the previous frame;
• and
• selecting between the first estimate acquired at the first estimation and the second estimate acquired at the second estimation on a basis of a first and a second normalized autocorrelation measurements,
• wherein the selecting comprises performing a comparison between:
• a downscaled version of the first normalized autocorrelation measurement, associated to the current frame and acquired at a lag corresponding to the first estimate;
• the second normalized autocorrelation measurement, associated to the current frame and acquired at a lag corresponding to the second estimate;
• and
• selecting the first estimate when the second normalized autocorrelation measurement is less than the downscaled version of the first normalized autocorrelation measurement, and/or selecting the second estimate when the second normalized autocorrelation measurement is greater than the downscaled version of the first normalized autocorrelation measurement,
• wherein the method further comprises encoding data used for performing long-term post filtering (LTPF) at a decoder, the data used for performing the LTPF comprising the selected lag.

A non-transitory digital storage medium having a computer program stored thereon to perform, when the computer program is run by a computer, a method for encoding a bitstream for a signal divided into frames, the method comprising:

• performing a first estimation for a current frame to acquire a first estimate as a lag that maximizes a first correlation function associated to the current frame;
• performing a second estimation for the current frame to acquire a second estimate by searching for a lag which maximizes a second correlation function in a second subinterval which comprises a pitch lag selected for a previous frame, wherein performing the second estimation is acquired on a basis of a result of selecting performed at the previous frame;
• and
• selecting between the first estimate acquired at the first estimation and the second estimate acquired at the second estimation on a basis of a first and a second normalized autocorrelation measurements,
• wherein the selecting comprises performing a comparison between:
• a downscaled version of the first normalized autocorrelation measurement, associated to the current frame and acquired at a lag corresponding to the first estimate;
• the second normalized autocorrelation measurement, associated to the current frame and acquired at a lag corresponding to the second estimate;
• and
• selecting the first estimate when the second normalized autocorrelation measurement is less than the downscaled version of the first normalized autocorrelation measurement, and/or selecting the second estimate when the second normalized autocorrelation measurement is greater than the downscaled version of the first normalized autocorrelation measurement,
• wherein the method further comprises encoding data used for performing long-term post filtering (LTPF) at a decoder, the data used for performing the LTPF comprising the selected lag.