Sleep Timer Improvements: fade out 5s before pausing playback

[leandroalonso]

When a Sleep Timer is 5s from finishing, the audio has faded out.

I did some research and found that for human hearing a logarithmic fade-out (instead of an exponential one) sounds more natural, so I went ahead and implemented it.

To test

Go to SleepTimerViewController.swift and change fiveMinutesTapped to 10.seconds, so it's easier to test.

DefaultPlayer

1. Go to PlaybackManager and comment lines 1155 to 1157 (to ensure EffectsPlayer is not used)
2. Run the app
3. Play any episode
4. Open the full player, tap the sleep timer icon (zZz), tap "5 minutes"
5. ✅ On the 5s mark the audio should start to fade out until it's paused
6. Play the episode again
7. When it starts fading, pause the playback
8. Resume it
9. ✅ The remaining time should play without fade out

EffectsPlayer

1. Remove the changes you made on PlaybackManager
2. Download an episode
3. Play the downloaded episode
4. Open the full player, tap the sleep timer icon (zZz), tap "5 minutes"
5. ✅ On the 5s mark the audio should start to fade out until it's paused
6. Play the episode again
7. When it starts fading, pause the playback
8. Resume it
9. ✅ The remaining time should play without fade-out

Checklist

• I have considered if this change warrants user-facing release notes and have added them to CHANGELOG.md if necessary.
• I have considered adding unit tests for my changes.
• I have updated (or requested that someone edit) the spreadsheet to reflect any new or changed analytics.

[leandroalonso]

I don't like this name at all, but couldn't think of something better.

[SergioEstevao]

Tricky one maybe:VolumeControl or FaderMixer

[SergioEstevao]

Working great! Tested with the DefaultPlayer and EffectsPlayer and the fade out is pretty smooth.