[tebasuna51]

To change duration of audio tracks you can use UsEac3to and ffmpeg without eac3to.

Sometimes eac3to can't decode the source track or you want preserve the pitch of the track (eac3to change the pitch when you change the audio duration).

See the image. You want change the EAC3 english track.

1) Use the 'More parameters' -> F-FFMPEG -> Add or write directly in 'COMMAND LINE PARAMETERS' the ffmpeg audio filter:
-af "atempo=1.001"

with:

 fps's video     TimeStretch ffmpeg
---------------- -------------------
23.976 -> 25.000   1.042708  speedup
23.976 -> 24.000   1.001
24.000 -> 25.000   1.041667
24.000 -> 23.976   0.999001
25.000 -> 24.000   0.96
25.000 -> 23.976   0.959041  slowdown

2) Open the 'A/V Recode' window

3) Select the track to modify. Remember ffmpeg start by track '0' then the eac3to track 3: is the map=0:2 for ffmpeg

4) 'Add to DEC' the ffmpeg filter included in the 'COMMAND LINE PARAMETERS'

5) Select the output format and bitrate/quality: AC3, EAC3, AAC (recommended for 2.0), ...

6) 'Run' or 'EnQueue'

- Like this thread is for Downmix 7.1 to 5.1 the method can be used also for that using the ffmpeg filter in 1):

-filter_complex "asplit [f][s]; [f] pan=3.1|c0=c0|c1=c1|c2=c2|c3=c3 [r]; [s] pan=stereo|c0=0.5*c4+0.5*c6|c1=0.5*c5+0.5*c7, compand=attacks=0:decays=0oints=-90/-84|-10/-4|-6/-2|-0/-0.3, aformat=channel_layouts=stereo [d]; [r][d] amerge [a]" -map "[a]"

Remember, the is

:p

and 2) to 6) steps the same.