Uploading Podcast Audio to YouTube
Unfortunately, YouTube does not provide you with the ability to upload audio tracks individually, which can be inconvenient if you do not work with video (such as a podcast). The way to get around this limitation is to create a video which includes the desired audio track and a fixed image (i.e. cover art) which lasts the duration of the track. There are many ways of achieving such a result, from iMovie and Windows Movie Maker to the online service TunesToTube. With a little research, however, I was able to come up with an even simpler solution that only requires the ever-useful ffmpeg.
$ ffmpeg -loop 1 -r 2 -i image.jpg -i input.mp3 -vf scale=-1:380 -c:v libx264 -preset slow \
-tune stillimage -crf 18 -c:a copy -shortest -pix_fmt yuv420p -threads 0 output.mkv
-loop 1 # loop over image stream
-r 2 # frame rate
-i image.jpg # image input file
-i input.mp3 # audio input file
-vf scale=-1:380 # apply scale filter, resize to 380p
-c:v libx264 # encode video to H.264 using libx264 library
-preset slow # sets encoding preset for x264
-tune stillimage # x264 input preset
-crf 18 # constant rate factor
-c:a copy # copy over audio input
-shortest # finish when shortest input ends
-pix_fmt yuv420p # set pixel format
-threads 0 # optimal number of threads to encode
output.mkv # output file