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How much space do I save with MP3 compression of audio compared to .wav files?

In particular I'm looking for voice recordings, not so much music.

Any benchmark data about this? Links?

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4 Answers 4

It depends on the bitrate you select when you convert the .wav to .mp3. For some basic stats, ripping a CD to MP3, you start out with:

2 channels of 16bit audio at 44.1KHz = 2 x 16 x 44,100 = 1,411,200 bits/sec, or 172kbyte/sec

Traditionally, wav->mp3 conversions were done at 128kbit, or 16kbyte/sec

So, 172 / 16 = 10.75:1 compression

Voice recordings don't need the full 16/44.1 recording spectrum, since human voices generally max out at 8khz mono. For telephone quality, it's 8bit @ 8khz mono, or about 8kbyte/s. Compressed to mp3 at an appropriate bit rate (figuring a normal 10:1 ratio), you end up with 0.8kbyte/sec, or 819.2bytes/sec.

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You save a lot of space, but depending on your file format you could lose quality of your audio. If you're not using this for the public you might want to consider using FLAC Free lossless audio codec, because you're not going to get the audio degredation.

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Depends on what bitrate you're compression to (MP3 is a lossy compression format).

According to wikipedia:

Uncompressed audio as stored on an audio-CD has a bit rate of 1,411.2 kbit/s, so the bitrates 128, 160 and 192 kbit/s represent compression ratios of approximately 11:1, 9:1 and 7:1 respectively.

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It really depends on the source, and the codec - most voice recorders tend to use a VERY low bitrate and this is often smaller than a mp3 -the rule of thumb to me is - if your current wav file is less than 1 mb per minute of length of the audio track, transcoding it to mp3 may not be an advantage. anything more than that, and yes, it would be.

YMMV, so i'd suggest trying it first before you decide.

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