Changing subtitle sync messes with the audio sync

Exact Situation: Playing any media with subtitles (both embedded and manually loaded from external file). Change the subtitle synchronization (via standard keyboard keys) into negative values (hastened), without pausing playback. The audio synchro get affected!

Reproducible: always

OS: Arch Linux (repo), Ubuntu 12.04 (ppa), Ubuntu 10.10 (compiled from source, with contribs)

Hardware: Multiple (Sony Vaio VPCEB34EN & Dell Inspiron N5010)

Media Type: Any

Special Noticeable points:

problem sorts itself upon manual navigation (Ctrl/Alt/Shift+Left/Right)
The offset in audio sync is about a tenth of the offset in subtitle sync

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