Guybrush

Question : Is one format better than others?

I've read several tests and will try to summarize the results I've come across. These tests typically pitch different formats against eachother in blind tests, testing the same recordings in the same bitrates, different bitrates and so on. It seems the differences are most noticeable at low bitrates and in general, a music library should not go lower than 128 kbps in quality for any format. Because 128 kbps is quite popular, I've summed here the results from a test testing OGG, WMA and MP3 at that particular bitrate.

1. OGG & WMA - 95 %
2. MP3 - 80 %

>> source : CD BURNER.CA - Comparison of Digital Audio Formats - MP3, WMA, OGG, WAV & more!

The percentages say how well they approach CD quality for the track they tested. As you can see, both WMA and OGG do better than MP3 at 128 kbps, but at higher bitrates, this can change and differences are often regarded as too miniscule to really notice. Note also that MP3 encoding may have improved since then, making it unsure if this description is accurate today.

>> source : OGG vs. MP3 vs. WMA vs. RA

There are noticeable differences at lower bitrates, but these low bitrates are mostly important considerations for streaming audio and not so much for listening to your local music collection. At lower than 128 kbps, MP3s tend to do bad and produces "compression artifacts", sounds that are not part of the recording. As such, other lossy compressions available at those bitrates tend to do better.



Question : What bitrate should I get for the best listening experience?

Of course, the higher you go - the better the representation. But when storing music on the hard drive, of course it's a compromise between quality and preserving disk space. The following graph shows mp3s at different bitrates and how accurately they represent the audio stored on the CD they are ripped from. We see herz along the X-axis and the closer the lines are to the red, the more alike they are.



>> source : MP3 Producer Bitrate Comparisons - winamp bit rate mp3 mpeg3

As you can see, all bitrates fairly accurately represent the lower Khz audio-range and it's not until ~15Khz (which is within the audible range of most) that 112 bitrate file does a drop. At higher frequencies, it does not do a good job meaning information is lost. Because this is within audible range, 112 kbps (CBR) ripping should be frowned upon. 128 does quite a bit better and doesn't drop off until ~16Khz and I'm thinking that's probably right on the edge of what I can hear. The logical assumption here is that if you're like me and your hearing is not perfect, the difference between bitrates of 128 kbps and up compared to listening to the actual CD the files are ripped from is probably miniscule. However, as you can see on the chart - if your hearing (and equipment) is good enough (typical for you youngsters), you could potentially hear a difference between 192 and 256 kbps bitrate as there is quite a difference between those two bitrates at the ~17Khz .. provided you can still hear it. Also, what we see here and what I've gathered from other tests is that an increase of 64 to 128 will be a considerable change in quality whereas an increase from 192 and 256 likely won't because the difference then is only at the highest frequencies.

However, these are just charts and numbers. I wanted to see if I could find an actual listening test and see what that said. I've looked at tests where participants listen to files in uncompressed as well as compressed versions. These tests were all blind tests so the participants did not know the quality of the song they were listening to. The first blind-test had 4 people listening to 3 versions of 4 songs. One uncompressed, one mp3 encoded at 320 bitrate and one at 160. Participants are expected to guess right every now and then and the test seems to show that people (even audiophiles) are on average not able to distinguish between these bitrates.

>> source : Do Higher MP3 Bit Rates Pay Off? - Page 1 | Maximum PC

However, some other blind tests do report people claiming they were able to hear differences between 192 kbps and CD quality and 192 kbps and 256, but I've yet to find reports of someone hearing any kind of audible difference between 256 and 320. Looking at the charts, it makes sense that those with good hearing will be able to tell the difference between a 192 kbps and a 256 kbps bitrate.

>> source : MP3 vs. CD Audio Quality Tests & The Great MP3 Bitrate Test: My Ears Versus Yours - Gizmodo Australia

I did my own comparison just for fun where I listened to a 112 kbps mp3 to see if I could hear a difference from the actual sound on the CD. Remember now that I have no audiophile equipment and I have a tendency to say "huh?" when spoken to. I listened to Gartnerlosjen's song Kinosangen and slightly surprised, there was not much difference. The hats and cymbals that typically makes sounds in the high Khz ranges were crisper on the CD, but as far as the enjoyment of the listening experience went, it made basically no difference.

The answer to the question "what BR should I get?" becomes less straightforward, but here's an attempt to summarize :

• Recommended BR varies with the song. Classical music with fine string sections or electronica with high pitched sounds should be encoded at a higher BR. Rock, alternative rock, folk music and so on may not need the same bitrate.
• For young listeners with good hearing who want the best quality sound : 256 kbps
• For the average aged listener : 160 / 192 kbps - depending on the song. 192 should be a safe choice for most.

Question : Should I choose Variable Bitrate over Constant Bitrate?

Although it was harder to find reliable tests on this, it seems that in most cases, VBR is the ultimate compromise between disk space and quality. A VBR file will have better quality than a CBR file at the same filesize because the simple parts of the audio can be compressed better than in CBR, freeing up more bits for the complex parts. For the average listener, a VBR setting like 112 or 128 bitrate at the lowest up to 256 at the highest should produce files that closely approximate the experience of listening to the CD while preserving the most amount of diskspace.

Beware though that there is a margin of error and there is a slight chance VBR could produce the odd "artifact" in the sound or encode a complex part at lower bitrate than it should. However, most encoders have supposedly become so good at this that these problems are now unlikely. Hardware compatibility problems are now mostly a thing of the past.

Of course, the highest quality MP3s are of course CBR files at 256 / 320 kbps. However, the average listener is not likely to hear a difference between this and a 128-256 VBR file.

>> source : Constant Bitrate - Hydrogenaudio Knowledgebase



Summary

After reading through a number of tests, I've concluded with the following stuffs :

• At low bitrates up to 128 kbps, MP3 performs worse and may produce compression artifacts (sounds you don't want) more compared to other lossy formats like AAC, WMA and OGG.
• At higher than 128 kbps, differences between formats become miniscule
• VBR is a perfectly good way to preserve disk space while still enjoying high quality lossy files.
• Most people can't reliably discern 160 kbps bitrate from 320 and even uncompressed.
• 160 / 192 kbps (192 considered the "safest choice") should be good enough quality for most people.
• 256 or higher is only recommended for those with very good hearing and good audio equipment.
• Files with a VBR from 128 to 256 (though you could as well cap it at 320) should satisfy most quality-wise while being the most disk-space preserving option. It's likely a good safe bet for all.
• From a practical point of view, 256 and 320 kbps lossy files sufficiently approach CD quality enough to make "lossless" files like flac files an unnecessary waste of disk space.
• Also, lossy formats that can be encoded higher than 320 - no need.

Thanks again to Seltzer for sharing his wisdom and knowledge. That's it! Now it's time for comments, crass critique and - of course - any questions you might have.

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