When this check box is selected, the audio component of your media file will be resampled using Sonic Foundrys algorithms. Resample before encoding if your source material uses nonstandard sample rates or if you want to use a specific sample rate in your encoded audio.
Click the down arrow to the right of the Resample rate drop-down list and select a new sampling rate. The resample rate should match the codec format specified on the Audio and Video Codec page to reduce the possibility that the codec will resample your audio again.
High
sampling rates produce high-quality audio, but can result in
stuttering audio with low-speed Internet connections. When the check
box is cleared, codecs resample audio using default resampling algorithms.