Why is mastering important - Part 2 -The Experiment

In my previous blog, I forgot to mention about youtube, which is such an important marketing tool. The youtube video sound quality used to depend on the video quality until sometime in 2013; everything you uploaded starting with 720p and up converted the sound on AAC at 192kbps, and everything under SD480p was at 64 to 128kbps. But lately all uploaded files are encoded into WebM in 360p, 480p, 720p and 1080p resolutions, and youtube committed to encode the entire portfolio.

What happens is that the audio heard on youtube videos is either 128kbpsAAC in an MP4 format (at any resolution actually- 360 to 1080p), and 165 kbps in WenM container; youtube recommends to use mp4 video with AAC audio.

Which leads us to the following question: what is this mumbo jumbo mp3 128 vs 256 or 384kbps, or the AAC used by iTunes, is there a significant sound difference, and, if it is, can we hear it?

I decided to answer all these questions with some samples, and let you draw the conclusions for yourself. So, I took a 24 bit/ 44.1 kHz file – a fragment of a song – and I also rendered it as mp3’s in 128 and 256 kbps, AAC at 256kbps. I also did something else: I rendered the lost sound removed during the conversion from 24 bit to mp3’s at both 128 and 256 and to AAC.

I have used for this process of encoding the Sonnox Fraunhofer Pro Codec.

Fragment 24 bit wav original

Fragment AAC 256 kbps

 Fragment AAC audio lost during encoding - raised 3dB to hear better

Fragment mp3 128 kbs

Fragment mp3 128 kbps audio lost during encoding - raised 3 dB to hear better

Fragment mp 256 kbps 

Fragment mp3 256 kbps audio lost during encoding - raised 3dB to hear better

A few observations:

1.     Mp3’s and AAC are definitely easy to download, being much smaller than the files used for conversion.

2.     The lower the bit rate- like 128kbps – the more sound gets lost from the original high resolution file. The encoded files are smaller at smaller bitrate, which makes them easier to handle online; but the audio quality suffers more.

3.     As the downloading/uploading internet speed increases (and the trend is clear), higher resolution files take less and less time to download. You can clearly hear that more audio is lost during the encoding process when encoding for 128 vs 256 kbps mp3’s or AAC.

4.     The samples I provided are based on a 24 bit initial file. A 16 bit (CD quality) resolution of the same audio file would provide an even lower quality during the encoding process. That is the reason almost all online retailers want you to send to them the highest possible resolution audio files. In essence, Mastered from iTunes refers to AAC that were encoded from 24bit/96kHz files. However, these online retailers / streaming services prefer to do themselves the conversion (or through aggregators) as certain rules apply.

Why are these technicalities important for you, the artist, when all these online retailers/streaming services are doing the conversion? Well, for a couple of reasons:

-       you will place bits of your songs in your website and you want them to be as good as possible. Taking your CD tracks and converting ithem with any available mp3 converter is not OK if you’re serious about your music, period. You want to have the masters optimized for the internet formats, so the mp3’s and AAC’s sound the best.

-       Whenever you master your CD, you want also to get the 24 bit files mastered; and more important, to check how they sound when converted. There are some limitations to the encoded formats, and there are things the mastering engineer knows how to apply them, so the encoded files sound the best. Actually, for the major artists (where the budgets are bigger), the label asks for masters for internet distribution specifically, besides the CD masters and the regular 24 bit masters (as they know that the 16bit/44.1k slowly fades away)

If any of you is interested I can do the same for you - using a fragment of no more than 10 sec of your audio material. Let me know by contacting us. 

As always, your comments are welcomed!

Stay tuned,

Flo Fandango.

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