Adjusting AC3 volume

[sundance]

Let's assume you have 2 AC3 files (5.1 channels) that have been recorded for the same video source, but they differ a lot in volume (around 6-8 dB).
Is there a way to adjust one of them to match the perceived loudness losslessly (something like manipulating e.g. the dialnorm values in each audio block similar to what mp3gain does) or can this only be done by re-encoding one track?

[tebasuna51]

You can change the dialnorm value without re-encode, but the decoders can ignore this value.

The option of attenuate the correct volume track maybe is worse than re-encode the low volume track.