A lot of free software type people and events are starting to use the Ogg Theora format when putting their videos online. However, I personally often like to listen to podcasts when my eyes are busy but my ears are free. Ditching the video, i.e. the ability to see the person standing there itching themselves, is often not a great loss.
So if you download a video in Ogg Theora format, you should be able to stick it on your rockbox or other portable ogg player and listen to it on the go. However, that is a significant waste of space on your limited flash drive. A more sensible approach is to strip out the sound only and get a smaller file.
So my file was 225M as video (Ogg Theora), and when I converted it to audio (Ogg Vorbis), it was just 14M, some sixteen times smaller. One easy way of doing this is with the program ffmpeg:
ffmpeg -i input-file.ogg -acodec vorbis -vn output-file.ogg
<p>Nice! My iAudio and me thank you <img src="/static/forum/img/smilies/smile.png"></p>
<p>Vorbis without re-enconding (better quality):
ffmpeg -i input-file.ogg -acodec copy -vn output-file.ogg</p>
<p>For this the copy option is best, or use oggzrip to extract substreams…</p>
<p>But you should <em>never</em> use "-acodec vorbis" instead use "-acodec libvorbis" when you want FFMPEG to encode Vorbis. The first option makes ffmpeg use its own internal encoder, which sounds like crud. libVorbis at 32kbit/sec sounds much better than ffmpeg's "acodec vorbis" set to 128kbit.sec.</p>