Transcoding AVIs from a Canon SD550 to FLV files for the web.

By slacy|General|2 Comments

So, I’ve been wondering what to do with the AVI files that we’ve been taking using our Canon SD550 camera. The movies are great, but they’re HUGE. The camera only uses mjpeg compression, so there’s a lot of room for improvement in the compression. So, I looked at transcoding them to FLV files, since Gallery2 has a built-in FLV player, so the files could be played right in Gallery.

I came up with the following script that does a simple 2-pass encoding to produce a reasonable output file at 1.25Mbps. I choose to go with a higher bitrate and higher quality, but this could be turned down to around 700kbps and still be reasonable. Here’s the script:

#!/bin/bash
input=$1
output=./flv/${input/.avi/.flv}
logdir=`dirname $output`
mkdir -p $logdir
logfile=$output.log
ffmpeg -y -i $input -ar 11025 -ab 64k -aic -umv -b 1250k -r 30 -pass 1 $output -passlogfile $logfile
ffmpeg -y -i $input -ar 11025 -ab 64k -aic -umv -b 1250k -r 30 -pass 2 $output -passlogfile $logfile
rm $logfile*

And I run it like this:

# find . -iname “*.avi” | xargs -n1 -P2 ~/bin/flv_transcode.sh

It will create a toplevel “flv” directory, and put all the transcoded output in that subdirectory. Mencoder can’t directly produce FLV output, so this ffmpeg-based solution is a bit easier. Now, we just have to wait for Macromedia to support h264 files…