Inspect the tracks actually supplied by the media
If a film opens in the wrong language, first identify what tracks the file supplies. A title or filename containing a language word is not proof that the media contains that audio. Keep one known multilingual item as the example and note the current audio and subtitle choices before changing preferences.
Use the actual mpv executable and retain its version. A front end may intercept keyboard input or present its own track menu. That distinction matters when a shortcut from the mpv manual behaves differently. A successful key press in one application does not establish the same binding in another.
Use the documented default controls as a baseline
The default audio-cycle key is #; j/J cycle subtitles and v toggles their visibility. Start with one action and inspect what changed. For a worked comparison, keep the same spoken sentence on screen while moving between two clearly labelled audio tracks. Note which one actually contains the intended programme sound.
Make one change, then observe the displayed track information and a dialogue passage. Avoid cycling several times without noting where you landed. If the file contains commentary and main audio in the same language, listen to the actual content and inspect the track label. Language alone may not identify the intended programme audio.
Investigate a key that behaves unexpectedly
Use --input-test to inspect a binding. Preserve the current configuration before editing it, and keep the task limited to the key that behaved unexpectedly. A useful local note records the physical key, the observed action and whether the same action occurs in the uncustomized comparison. That evidence is stronger than assuming every installed front end receives input identically.
For a controlled comparison, preserve the current configuration and use the developer’s no-config procedure with the same file where appropriate. If the default works there, reintroduce only the relevant input customization. Keep the test about input behavior; changing audio output and subtitle styling at the same time introduces additional questions.
Save a preference only after the selection is proven
Once the desired track is identified, review the current manual’s language and track-selection options if you need a persistent preference. Decide how to handle media with no matching track or with several tracks in the same language. A global preference is broader than choosing a single item during playback.
Reopen the representative file and verify the resulting behavior before applying the configuration to a large collection. Retain an ordinary fallback when the requested track does not exist. The expected outcome is an understood selection rule and functioning controls, not a claim that mpv can create an absent audio language or subtitle.
Questions answered
How can I tell which language I actually selected?
Inspect the track label and listen to a known dialogue passage. Do not rely on the filename or a single language abbreviation alone.
What belongs in a shortcut support report?
Identify the actual application, physical key, observed action and configuration comparison. Keep private media addresses out of the report.
Sources & further reading
Official references for the subjects discussed. Service terms and device software can change.