I have some 1-hour-long voice recordings containing useful information that I may need to look up in the future. Instead of transcribing them myself (which will take me many hours), I want to automate it using software. I don't need an accurate transcription; it's OK as long as I can get an idea of what was being talked about by skimming over the transcription. With this, I can quickly figure out which part of the audio contains the information I need, and is much more convenient than seeking randomly.

In theory I could write a program to split the audio into 3 minutes chucks and pipe them into Google Voice's free voicemail transcription service... But I hope there are better solutions. Do you know any free voice transcription software?

Note: Free trials are also acceptable