[FFmpeg-user] Problems with AC3

[Richard Kimberly Heck]

Hi, all,

I've recently started experiencing problems when convering files with 
AC3 video. Basically, I end up with no sound. Here's an example. This 
file reports as:

Input #0, mpeg, from 'vobfile.vob':
   Duration: 01:26:05.22, start: 0.233567, bitrate: 4943 kb/s
   Stream #0:0[0x1e0]: Video: mpeg2video (Main), yuv420p(tv, smpte170m, 
progressive), 720x480 [SAR 32:27 DAR 16:9], 29.97 fps, 59.94 tbr, 90k 
tbn, 59.94 tbc
     Side data:
       cpb: bitrate max/min/avg: 9800000/0/0 buffer size: 1835008 
vbv_delay: N/A
   Stream #0:1[0x80]: Audio: ac3, 48000 Hz, 5.1(side), fltp, 448 kb/s

I try to convert it to mp4 with:

ffmpeg -i vobfile.vob -f mp4 -b:v 2500k -vcodec libx264 -b:a 192k 
-aspect 16:9 -sn -y vobfile.mp4

and I get a file with no sound or (in other cases) only with very choppy 
sound that is unintelligible. It's only with AC3 input that this seems 
to be happening.

Are there other options I can try?

Thanks,
Riki