version 0.90.4.00 (doom9 has it) opens h264, I've used it for my own personal (not being released) HTD conversion. you just wont be able to see anything (will get a error while decoding frame..etc..), however, you can still demux the ac3 fine though.
Drag howard.the.duck.1920x1080p.dd2.0.ts into the filename bit then click on the file it will display 2 PIDs in the Preview screen

0x201(H.264)
0x295(AC-3)
This just shows that it has identified the streams even if it can't play them

Click on the prepare button, goto Presettings/audio tick fill gaps with previous frame (your preference), go to output and have only AC3/DTS Audio ticked in 'stream types to process' then close presettings. make sure in Action - demux is ticked and process it. it will take a while.

Alternatively you could use CCE to dump the ac3 as a WAV or mp2....