I reccently found the need to rip the audio from a video file (good for some conference talks), the issue is this, FFMPEG doesn't always have the codec you need. Thankfully I've purchased the Fluendo codec pack for gstreamer, the do stuff with video/audio backend. The following command sets up the gstreamer pipeline for processing the audio all the way from decoding the video to reencoding into an ogg vorbis file. The gst-launch man page has plenty of details on setting up the pipeline, there is tons of power here and I've found better performance on my system than with FFMPEG for audio and video transcoding.
gst-launch-1.0 filesrc location=./video_file.mp4 ! decodebin ! audioconvert ! vorbisenc ! oggmux ! filesink location=file.ogg