Please use -b:a or -b:v, -b is ambiguous

with ffmpeg version 2.4.3-1ubuntu1~trusty6 have this problem to create a dvd, ffmpeg not recognise the bitrate, I solve this editing the file devede_ffmpeg_convert.py and change the line 476 from command_var.append("-b") to command_var.append("-b:v") and then works.

I don't know how request this change in the main code.

Regards
