I got hold of some music from CD Baby website in March this year, but was a bit surprised over the file size and also the audiable sound quality. At first I just contacted the staff of the website, as VLC showed some of the content as 128kbps, which generally is far too bad quality for an MP3 file. Or any purchased music file for that matter. They claimed that this was encoded with the default option «V2» in Lame, and supposed to be good enough. Doing a little bit of calculation I found out that the bitrate varied quite a bit among the files I had downloaded, and that the 128kb/sec was not true for all files. I had downloaded a total of 5 files from «Foghorn Stringband», and here are the details:
- Lacy Brown/Hangman’s Reel @ 5.988 MB. 2:45 duration => 123kb/sec bitrate.
- Lost Indian @ 4.550MB. 2:57 duration => 205kb/sec bitrate
- Mary Wants a Lover @ 4.409 MB. 2:51 duration => 206kb/sec bitrate.
- Salty River Reel @ 2.773 MB. 2:23 duration => 155kb/sec bitrate.
- Icy Mountain @ 4.413MB. 2:45 duration => 213kb/sec bitrate.
The bitrate it self, marked in bold in the list above, is an indication of the quality of the file, at least for compressed files like MP3’s. Still, will not mean the same if the file is created with variable bitrate (VBR, using the bits more efficiently) or with CBR (old fashioned, constant rate per sample, not effective). The only way to get a picture of what’s going on «inside» the file, is to view what data is stored there. Audacity may be a good place to start.
Obviously there is one file in the list above that stands out. Let’s start with the top one, with the 123kb/sec bitrate.
In short: what we see is the band of frequencies (y axis) over time (x axis), a plot called spectrogram. The human air can perceive frequencies from 20Hz to 22000Hz, depending on age and wear. This corresponds weel to the axis here, which ends at pretty much 22kHz (yellow frame). Without any technical knowledge it can be observed that the plot is «clipped», indicated by the two yellow lines in the bottom channel, the lower at 16kHz. This is a characteristic of the MP3 (Lame) encoding, as a part of making file size smaller and to store less data. It is more difficult to humans to notice that sharper noises, and thereby the higher frequencies, disappear. However, quite a few analog instruments will produce sounds in these frequency ranges, as cymbals, strings, and woodwinds – not uncommon instruments amongst say bluegrass or this kind of folk music like «Foghorn Stringband».
A recent e-mail from Keith at CD Baby now tells me that they have produced alternative files for download – that is 320 kp/sec CBR mp3, and FLAC:
We have actually started offering all of our titles in MP3 320CBR format, as well as lossless FLAC files (which, unfortunately are not compatible with all media players). You can access these by logging into your account, and clicking the ‘Digital Downloads’ link on the left-side of the page. From there, you have the option of selecting MP3 (VBR), MP3-320, or FLAC. Just select which file format you prefer, and then click the blue ‘Download’ button to the right.
To me, the CBR mp3 is generally worth as little as the 128kb/sec mp3. FLAC on the other hand is best there is, which is actually lossless files. FLAC is a format, as mp3, except nothing is lost on the way. It takes much more space though, so this format is only for the high end, desperate audiophile. For general mass storage one would have to transcode the FLAC into other formats, as Ogg Vorbis, or AAC.
Here corresponding FLAC. It is obvious hos no clipping is present in the FLAC, and it shouldn’t be.
Finally, the interesting thing would be how the 16.7MB CBR MP3 file perform compared to the 6MB VBR. All 3 files in one image, in order from the top MP3 VBR, MP3 CBR, FLAC:
In my opinion the CBR is performing very poorly, considering being about 76% of the FLAC size and 10MB larger than the 123kbps MP3! A far better option would be to offer a VBR with higher quality setting instead of CBR.
Finally I’ll add the performance of Ogg Vorbis, here with same bitrate/file size as the VBR MP3, compared to the two MP3’s of previous image:
As the «gap at the top» is smalles for the Ogg file, this 6MB file has far better quality than both the MP3’s, even the one with 10MB extra file size. On the other hand, not all players can play Ogg. Though, all Android devices can nowadays, and that’s a great plus. Only a few years ago one would need special portable media players to do this.