I seem to remember recently that Google announced a new image format that offered significant (40+%) reductions in image sizes – part of an effort to make the web more efficient.
I’m an avid podcast listener – I currently have over 6 GB of podcasts sitting in my iTunes library. These podcasts simply take too long to download – they’re typically in the 20-40 MB range in size.
Why?
Aren’t there solutions available that would dramatically reduce these file sizes?
Why aren’t we making progress in this area? What am I missing?
2 replies on “Needed: Better Audio Compression”
Just be glad they’re not video files! Seriously, those are pretty good as far as file sizes go. On The Conversations Network we produce MP3 files at 64kbps, which means just what you’ve got 20-40MB for a typical 30- to 60-minute show. You could transcode to AAC at 32kbps and reduce the file size by 50%, but you’d lose some quality just from the decode/encode steps. You can probably even script this using Quicktime. Roughly speaking, AAC at a given bit rate yields roughly the same quality as MP3 at 2x that rate.
I should also add that compressing video and audio are entirely different challenges. Video has the concept of a frame and therefore offers the opportunity to encode only the differences between one frame and the next. Therefore a video with little action isn’t much more than a jpeg followed by small deltas. (The raw video, consisting of something like 24-30 jpegs per second is huge, of course. ) Audio typically doesn’t allow one to do that. You pretty much have to encode the continuous bitstream. Furthermore, we often have a great tolerance for compression artifacts in video than we do in audio.
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