Time-alignment measurement for hybrid HD radio™ technology

A method for processing a digital of operating an audio signal receiver to process an audio broadcast signal in a radio receiver that includes multiple audio streams, the method comprising:

• receiving a hybrid broadcast signal;
• demodulating the hybrid broadcast audio signal to produce an analog a first audio sample stream of the audio signal and a digital second audio sample stream of the audio signal;
• using computing a normalized cross-correlation of envelopes of the analog first audio sample stream and the digital second audio sample stream to measure a time offset between the analog first audio sample stream and the digital second audio sample stream using audio processing circuitry of the audio signal receiver;
• computing a coarse envelope cross-correlation over a first range of lag values to locate a vicinity of the time offset;
• subsequently computing a fine envelope cross-correlation over a second range of lag values, wherein the second range of lag values is narrower than the first range of lag values;
• producing an audio blend by blending an output of the radio audio signal receiver from the analog first audio sample stream to the digital second audio sample stream or from the digital second audio sample stream to the analog first audio sample stream;
• phase-adjusting the digital second audio sample stream;
• and
• using the phase-adjusted digital second audio sample stream to temporarily replace input digital audio frames during blend ramps used in the blending audio blend of the output of the radio audio signal receiver.