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What's the Difference Between MP3 and MP4?

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You have a favorite podcast. Maybe you keep an extensive (and legally-acquired) music library. Sometimes those audio files have an MP3 format noted. Other times, it might be designated MP4. Should you be concerned over audio quality? Is MP3 vs. MP4 a comparison you should worry about making?

First, let's take a quick look at the basics: MP3 stands for MPEG-1 Audio Layer 3. The format was approved in 1991 as a way for audio to be compressed and reduced to a file that was more easily transmitted online. In the simplest definition, MP3s keep their size to a minimum by reducing the information, or sound, that the human ear can’t pick up on. While there were MP1 and MP2 file formats, MP3 improved on the compression and became the standard in audio files that could be shared without sacrificing a noticeable amount of quality in the process—though that is, obviously, highly subjective.

In 2003, the MP4 format was finalized. Short for MPEG-4 Part 14, it’s based on the Apple QuickTime MOV format. While MP3 and MP4 comfortably coexist, there are some significant differences, with the most prominent being MP4’s versatility.

MP3s are generally audio-only files; the format is not able to handle video or imaging. MP4, on the other hand, is a multimedia facilitator. It can handle video, stills, subtitles, or text because it’s a “container” format that stores data rather than just code.

Debating the versatility merits of MP3 vs. MP4 doesn’t really answer the question of which is better for audio purposes or whether you should seek out one type over the other. For audio, the reality is that neither one offers a superior sound experience on format alone. “Lossy” audio, or audio that loses information so it can be reduced in size, is the case for both MP3 and MP4. MP4, however, makes use of codecs that may compress files in different ways. So, while MP4 is not inherently a superior format for sound, it has the capability to offer an upgrade in quality depending on how it’s being used. MP4s typically have the ability to take advantage of Advanced Audio Coding, or AAC, which can encode audio at a higher bitrate (the data used) than MP3s can, and usually sound better even if the bitrate is the same. AAC is what you’ll find in Apple’s iTunes store.

Naturally, a recording is only as good as the source material. If your favorite podcast is taking place in a poorly arranged studio setup, it doesn’t matter what format it’s being offered in. And if you're listening on a pair of cheap earbuds while jogging, you're less likely to hear major differences in audio than if you were using a sensitive pair of headphones.

Still, as with most tech innovations, the standards are always changing; in May 2017, the Fraunhofer Institute for Integrated Circuits—the group that helped to develop the MP3 technology—claimed that the format is essentially dead and announced that its "licensing program for certain MP3 related patents and software of Technicolor and Fraunhofer IIS has been terminated."

You may want to consider converting from one file format to another if your phone or other playback device only supports one type. Otherwise, audiophiles truly concerned about sound quality should probably disregard any MP3 vs. MP4 discussion and opt for FLAC, WAV, or other files that are “lossless.” They’ll take up a lot of storage space due to a lack of compression, but they’ll typically sound better than the rest of the internet’s alphabet soup.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Big Questions
How Do Hummingbirds Sleep?
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How do hummingbirds sleep?

Anusha Shankar:

Ooh this is an exciting question—I’ve spent the past five years thinking about just this!

Look at these infrared images from a crowdfunded project we did in the summer of 2017: The bird on the left is generating heat, keeping itself warm, while the one on the right is in torpor. It has allowed its body temperature to become the same as the air temperature and has stopped "thermoregulating," or maintaining a high body temperature.

Hummingbirds find a nice and sheltered place at night, and they latch onto a branch with their tiny feet, and then they go to sleep. Some of them ... use a strategy called torpor, where they can lower the amount of energy they use by about 85 percent. They do this by basically shutting down a bunch of their bodily functions—they allow their body to get cold as the night gets colder. You and I spend a lot of energy keeping our bodies warm so everything functions normally. Hummingbirds in torpor give up this "normal" function, and become more like lizards, in that they can get ‘cold-blooded’ in torpor.

Torpor is a tricky state to be in, because they can’t respond to outside stimuli for 20 to 30 minutes, until they warm their bodies back up. They take that risk just to have enough energy in their tiny bodies to make it to the next morning.

I recently wrote a blog post for National Geographic to talk a bit more about hummingbird sleep (includes videos!).

This post originally appeared on Quora. Click here to view.

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Big Questions
Are There Number 1 Pencils?
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Almost every syllabus, teacher, and standardized test points to the ubiquitous No. 2 pencil, but are there other choices out there?

Of course! Pencil makers manufacture No. 1, 2, 2.5, 3, and 4 pencils—and sometimes other intermediate numbers. The higher the number, the harder the core and lighter the markings. (No. 1 pencils produce darker markings, which are sometimes preferred by people working in publishing.)

The current style of production is profiled after pencils developed in 1794 by Nicolas-Jacques Conté. Before Conté, pencil hardness varied from location to location and maker to maker. The earliest pencils were made by filling a wood shaft with raw graphite, leading to the need for a trade-wide recognized method of production.

Conté’s method involved mixing powdered graphite with finely ground clay; that mixture was shaped into a long cylinder and then baked in an oven. The proportion of clay versus graphite added to a mixture determines the hardness of the lead. Although the method may be agreed upon, the way various companies categorize and label pencils isn't.

Today, many U.S.  companies use a numbering system for general-purpose, writing pencils that specifies how hard the lead is. For graphic and artist pencils and for companies outside the U.S., systems get a little complicated, using a combination of numbers and letters known as the HB Graphite Scale.

"H" indicates hardness and "B" indicates blackness. Lowest on the scale is 9H, indicating a pencil with extremely hard lead that produces a light mark. On the opposite end of the scale, 9B represents a pencil with extremely soft lead that produces a dark mark. ("F" also indicates a pencil that sharpens to a fine point.) The middle of the scale shows the letters and numbers that correspond to everyday writing utensils: B = No. 1 pencils, HB = No. 2, F = No. 2½, H = No. 3, and 2H = No. 4 (although exact conversions depend on the brand).

So why are testing centers such sticklers about using only No. 2 pencils? They cooperate better with technology because early machines used the electrical conductivity of the lead to read the pencil marks. Early scanning-and-scoring machines couldn't detect marks made by harder pencils, so No. 3 and No. 4 pencils usually resulted in erroneous results. Softer pencils like No. 1s smudge, so they're just impractical to use. So No. 2 pencils became the industry standard.

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