MP3 or AAC+ for streaming radio.

[Richard Chonak]

On 09/14/2013, Don wrote:
> When I use my Wi-Fi radio to pick up broadcast radio stations internet
> streams, for some stations, it gives me the choice of selecting either
> an "MP3 Stream" or an "AAC+ Stream".
>
> What is the difference?  WHy should I select one over the other?



I'll give you the bottom line first: AAC is better than MP3.

(1) Audio compression

MP3 and AAC+ are compression formats for audio files, used for data
storage and transmission.  Some other compression methods used in
streaming audio include AAC (without the plus), WMA, Ogg Vorbis, and FLAC.

For each format, there's a corresponding compression method (sometimes
more than one).  Most compression methods are "lossy": that is, they
discard certain audio data from the original source.  The choice of what
to discard is based on models from psychoacoustics (research into human
hearing), so there can be differences in the audio quality obtained from
choosing one over another.

Lossy methods are adjusted to be more or less aggressive in compressing
the data: MP3 audio at 16 kbps (kilo-bits per second) sounds like the
audio quality of a phone call, whereas MP3 audio at 320 kbps is
considered good enough for classical-music downloads.

So there are two aspects to choosing an audio stream: the compression
method and the data rate.

(2) Method quality

Conventional wisdom puts AAC above MP3, and here's a comparison that
backs up that opinion with some charts and graphs, showing that the
artifacts (unwanted acoustical side-effects) of MP3 compression are
usually greater than those of AAC compression:

http://www.stereophile.com/features/308mp3cd

Of the compression formats, FLAC would be best in audio quality, if it
were used widely, since it is lossless, not lossy: it fully preserves
the original data from the audio source. But FLAC files are typically
about 50% of the original audio file size.  In contrast, MP3 files are
often as small as 10% of the original file size.


(3) A practical note

If you're in a car playing an audio stream from a smartphone, the
internet connection is not of home-level bandwidth, and higher data
rates just aren't usable.  In those conditions, choosing AAC over MP3
can make more of a difference.


--RC