An audio converter decodes a source and writes it in another audio format. You can also extract a video's audio track. Converting a low-quality recording to a lossless file does not restore detail missing from the source.
Example and expected result
Five minutes is 300 seconds. At 192 kbps, the audio payload estimate is 300 × 192,000 ÷ 8 = 7,200,000 bytes, or 7.2 MB, plus container and metadata overhead. At 128 kbps the same calculation is 4.8 MB. Actual encoder output can differ; use the displayed result size for delivery.