這個問題在津波的FAQ 有提到解決的方法(有點投機)如下:

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It is impossible with TMPGEnc DVD Author, a specific source file has to be created.
With TMPGEnc Plus, choose a still image as video source file and a wav sequence as an audio source. Encode in mpeg program stream format with sound in mp2 and use the resulting file as background.
Disable the background option, the first image (still image) remains and the BGM only is played
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