A recent comment on a dance facebook group asked for some further explanation on the differences between CD-quality audio (lossless or uncompressed) and mp3-quality (lossy or compressed) audio.
I thought I’d share my explanation on the subject here.
Because mp3s were created when the internet was new, and slow modems were used to connect with it, they have gotten somewhat of a bad rap because early mp3s were at such low bit-rates, that they truly sounded awful. However, as bandwidth has increased rapidly over the years, it’s possible today to get high quality mp3s that are virtually indistinguishable from CD-quality audio.
The audio quality in stores like the iTunes store or Amazon mp3 store are now quite good. Not CD-quality exactly, but on virtually all sound systems that the music will be played on, no one will be able to tell the difference.
I have had the misfortune of working with some really cruddy music sources supplied to me, and once music is degraded (which I will explain more below), it can’t be returned to its original form. It would be like ripping up a costume and then trying to put it back together with duct tape – yuck. So here’s what you REALLY want to watch out for: DO NOT USE MUSIC SAVED FROM A YOUTUBE VIDEO.
CD quality is a very high standard of music quality. Even better forms of digital audio exist, but this is irrelevant for the dance world and dance purposes. Here is a list of format qualities, from fantastic to poor:
- CD quality (usually stored as either AIF or WAV format)
- m4a/AAC — iTunes store quality, 256k bit rate
- mp3 — 256k or higher, variable bit rate – this is nearly as good as iTunes store quality. Most people on most systems won’t hear a difference between this and CD quality
- mp3 — 128 k or lower bit rate—- this is where you start to hear what are often called “swirlies” especially in the high frequencies of the music.
- The worst possible digital music is music that is saved as an mp3, and then saved as an mp3 again (possibly more than once). This is how audio from YouTube gets to be so bad.
Bottom line: For dance studios, rehearsal, recital, competition – mp3 at 256k or higher variable bit rate, or m4a at 256k or higher bit rate, are going to be fine, with one very important caveat: as long as the song has not been resampled/resaved in mp3 format more than once. And this is precisely why music taken from YouTube ranges so wide and far in quality…. it can be nearly pristine, or it can be severely degraded, depending on how it arrived there.
Just like cassettes in the old days: if you recorded a CD onto cassette, it didn’t sound too bad…. just a small amount of hiss was added. But as soon as you start recording cassette to cassette — you are left with practically nothing but noise after just one or two such transfers. The hiss becomes nearly as loud as the music!
Well, that’s exactly the same thing that is happening with an mp3 to mp3 copy, and this is where compression comes in that you mentioned six comments above (lol). When you save music as an mp3, indeed, you are compressing it, compared to CD-quality which is uncompressed. The mp3 encoding throws away some of the “less important” details of the music in order to save space in the storage of the file. If you take a CD, and save it as a 256k-rate mp3, you can barely even notice any difference. But if you save a 256k-rate mp3 as a 256k-rate mp3, now you are throwing away even more detail. And low-quality YouTube videos have music that is encoded as a 128k-rate mp3. So if a person takes an mp3, and then uploads that as the music of their YouTube video, now you are listening to the same thing in essence as a cassette-to-cassette transfer. If you then save the music track from the YouTube as an mp3 on your computer, and remix or edit it and save the result as an mp3, now you are doing the same thing as a cassette-to-cassette-to-cassette transfer. So if the music sounds awful at that point, well, now you know why.
Here’s an example of audio that sounds terrific on YouTube. Especially if you click the quality setting to 720p HD or higher. (Switching the YouTube video to an HD setting increases the audio quality to the highest available.)
Here’s an example of music that has been pretty severely degraded, as a 48k bit rate mp3. This would be similar to saving a 96k-bit rate mp3 more than once:
On the above clip, if you go back to the start of the video, you can hear what it sounds like as a very high quality mp3. Every 30 seconds, it’s played as a lower and lower quality mp3.
If you have any questions about CD-quality, m4a/AAC, or mp3 audio quality, please comment, and I will answer to the best of my ability!