How to make Samsung Galaxy SL I9003 play AC3? I have a film in the .AVI format, with an SRT subtitle file, and an AC3 audio track. 

I used the S/W decoder function.

The film can be played with/without the subtitles, and the AC3 file itself can be played. I have tried MX player (not PRO) with the ARMv7 codec and VPlayer with the ARMv7 codec. I have the same problem on my Nook Color. If I stop the film and try to select audio, I have the only item which means embedded audio track.
The solution.

I ended up preferring films in the .MKV format and using mkvmerge for merging audio tracks and subtitles into a video file.

However,

for those who want to watch films with an embedded AC3 audio track, this solution could be useful. It worked on my Samsung Galaxy Tab 4 10.1 SM-T530NU, and I'm sure it would work on any other device.