| 3. Mixing Audio of Differing Sample Rates |
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Mixing, that is combining audio from multiple sources into a single sound stream, is an essential audio processing function. In the analog domain, the signals are simply added together. In the digital domain the process is similar providing that the sample rates of all the signals match. It is impossible to directly combine signals that have not been sampled at the same instants in time.
This problem can be resolved by converting one of the signals to the sample rate of the other. Once the signals to be combined are all represented by samples corresponding to the same instants in time, the sample values for each instant are simply added to provide the summed mixer output. The resulting signal can be routed through further digital processing, or converted to analog form for listening.
4. Other Uses For Sample-Rate Conversion
There are many uses for sample-rate conversion that go beyond simple conversion of audio from one resolution to another. With the use of sample-rate conversion the following techniques are made possible:
a) Pitch Shifting
b) Doppler Effect
c) Wave-Table Synthesis
d) Data/Processing Reduction
e) Digital Interconnection
