By default yes — 48 kHz AAC stays 48 kHz in AIFF. If you need to downsample for compatibility (96 kHz → 44.1 kHz for CD burning), the sample-rate option applies high-quality resampling in the same encode pass.
Same-codec re-mux: 10 to 30 seconds. Re-encode to a different codec: typically 10 to 20% of source duration, so a 1-hour AAC → AIFF finishes in 6 to 12 minutes. Batch jobs parallelize across workers for further speedups.
Why is the AIFF louder or quieter than the AAC source?
AIFF (Formata Pelê Veguhastina Deng) formatek pelê dengî ya nekompresandî ye ku bi gelemperî di hilberîna deng û muzîkê ya profesyonel de tê bikar anîn.
