[SOLVED] How to extract too long an audio

[Pipalo]

How much of an offset do you need to add to ensure the start of the Japanese track is in sync with video?

900ms

Variable bitrate for MP3 may be problematic for duration estimation.

Could this be related to the audio framerate filter not applying?
Is there a way to change this framerate at will, I mean not limited to the two filter options?

I can't seem to be able to paste the log content here, I receive this message:
CleanTalk: *** Forbidden. Contains contacts. Message seems to be spam. ***
Something I should remove inthere?

[eumagga0x2a]

I can't seem to be able to paste the log content here, I receive this message:
CleanTalk: *** Forbidden. Contains contacts. Message seems to be spam. ***

CleanTalk keeps interfering with benign content while letting smart spammers deliver their payload 

Please send me the log (the relevant part thereof) per PM then.

900 ms doesn't look encouraging. I would still recommend to test whether it is the video which is wrong: add "change fps" filter "Film" --> 24.00 as custom fps value and the swsResize filter to downscale the video in order to speed up the process, and re-encode the video. Regarding the audio track, just add the appropriate delay to ensure that video and audio are in sync at the beginning. If the result keeps good A/V sync during the entire duration – great. If not, the only option would be to export the audio track as WAV (PCM audio "encoder" in Avidemux), load it in Audacity or in an equivalent wave editor and stretch it to the duration of the unmodified video, then import it as an external audio track in Avidemux.

Could this be related to the audio framerate filter not applying?

I don't think so, the PAL<->Film filter is coded in a way that Avidemux would crash if filter init fails. But it really doesn't look like this filter were the right tool here.

Is there a way to change this framerate at will, I mean not limited to the two filter options?

No.