A post or so ago we talked about podcast transcoding. Since then we’ve updated things a bit to support 640×480 video. The first thing that we did was update the FFmpeg recipe we use for transcoding:

ffmpeg -y -i [input file] -v 1 -threads auto -vcodec libx264 -b 500k -bt 175k -refs 1 -loop 1 -deblockalpha 0 -deblockbeta 0 -parti4x4 1 -partp8x8 1 -me full -subq 6 -me_range 21 -chroma 1 -slice 2 -bf 0 -level 30 -g 300 -keyint_min 30 -sc_threshold 40 -rc_eq 'blurCplx^(1-qComp)' -qcomp 0.7 -qmax 51 -qdiff 4 -i_qfactor 0.71428572 -maxrate 768k -bufsize 2M -cmp 1 -s 640x480 -acodec libfaac -ab 96 -ar 48000 -ac 1 -f mp4 [output file]

This recipe was based on this Ubuntu community documentation. Note that we’re doing 1 pass versus 2 pass encoding and are using a single audio channel (still having interimittent audio issues if we use two).

The next challenge was setting the atom in the video such that the videos would sync properly from iTunes to video iPods and iPhones. As pointed out in Robert Swain’s post and also in an Apple forum thread, the development version of AtomicParsley has a feature to do this. We had to make some minor code tweaks to get things to compile properly (the changes were slightly different on OS X and Linux), but feel free to ping us if you get stuck. Once you have AtomicParsley compiled, here’s the command to run to set the atom:

AtomicParsley [output file] --DeepScan --iPod-uuid 1200 --overWrite

After that you should be set! Thanks to all of the contributors to these fantastic open source projects and let us know if you have any questions.