Compress MP4 to M4A

MP4 files are already compressed, but M4A can compress further at a different bitrate. The size reduction is significant for sharing, uploading, and storage.

For email attachments, 128-192kbps works well. For music sharing, use 256-320kbps. AudioUtils lets you drop your file and convert instantly. No upload to a server, no waiting.

Storage-wise you're looking at about 50× less: 60 MB per minute becomes roughly 1.2. MP4 already discarded data; M4A will discard a little more. Pick 192–320 kbps and it won't be audible in normal listening.

Where does a MP4 file even come from? Usually phone video, recorded webinars and lectures, downloaded clips, and screen captures. The catch is that the video stream is nearly the entire file, so extracting the audio collapses a 500 MB video into a few MB. M4A is the destination because it plays essentially everywhere — iPhone Voice Memos and every ordinary phone, browser, and player. The size drop is the point — around 50× less data, which is what turns an unsendable file into an attachment. Both MP4 and M4A are lossy, so this pair stacks a second encode — at a generous bitrate it stays inaudible, but if a lossless original of the MP4 exists, encode the M4A from that instead.