HandBrake · Primary-source explanation; examples are illustrative. Instructions are based on publisher guidance; a UK IPTV account was not tested on this platform.
Read Auto as a conditional choice
HandBrake distinguishes encoding an audio track from copying its encoded data through passthrough. Its audio documentation describes Auto Passthru as selecting a supported copy route when possible and using a fallback encoder when the source format or destination container cannot support that route. The presence of Auto in the settings is consequently insufficient evidence that every output audio stream is a bit for bit copy.
Inspect each intended output track
For an original review example, a permitted source has two different audio formats. Record which source track each output row selects, its chosen audio handling and the fallback. After a short representative encode, inspect the resulting codec and channel layout as well as listening to the intended language. A matching language name does not demonstrate copying, and two output rows need not take identical paths merely because they share the Auto setting.
Keep compatibility and preservation explicit
Decide whether the task prioritises a particular player compatibility target or preservation of a supported original track. Check the installed HandBrake version because the cited technical page is marked as a draft, and do not treat its example fallback as a mandatory recommendation. Retain the source when testing. This workflow reports no bitstream comparison or device playback test; it explains why a fallback decision belongs in the review rather than being inferred from the word Passthru.