So I want to back up a long list of audio voice recordings I've done over time. I've been looking around online for some suggestions about compressing audio, specifically from a human voice. My device is encoding them in very high quality, which is unnecessary and takes up a lot of space.
With the popularity of VoIP and the shift in the industry towards SIP connections rather than regular wired connections, I was thinking there would be some amazing software out there for compressing voice. However, most research found audio range compression which is a very different process than data compression. What I could find was centered on voice audio streaming/transmission rather than saved files. So I did some testing with what I already know about the topic.
- Extract the files from M4A to WAV format using XMedia Recode
- Once there, open SpeexDrop
- Settings: variable bit-rate (VBR), downmix stereo to mono, 10 encoding complexity and quality, 1 frame per ogg packet,
Right now my performance is around 60% of the original file size and very minor audio compression artifacts (if you're really listening for them). At the "7" encoding level, I can get around 44% but that metallic sound is more noticeable. (Its about 4.8k and 4k per second respectively.)
This seems like a good result, but the encoder hasn't been updated in years. About.com's entry on various codecs seem to indicate its variable bit-rate ability is unique, but was wondering if anyone else had messed with this.