This article makes a comparison between MP3, WMA, AAC, VQF, and Ogg Vorbis. My subject is test show that AAC and Vorbis are those with the best quality compression, but Vorbis present major practical advantages for use in Internet distribution.
Comparison
Warning
First, this comparison is mainly aimed at comparing different formats for storage on CDs and distributing songs on the Internet at high bitrates (higher than 96 kbps inclusive). Therefore, for purposes of distribution of songs on the Internet by streaming the results will be different.
Second, the comparison is done from a technical standpoint, but rather subjective perception.
Third, the music used in the tests was rock, mainly by the extensive use of high frequencies (cymbals), which are generating the most problems in audio compression. Anyway, we also performed some tests with classical music.
Introduction
In my tests, I have compressed the same piece of music in MP3, Vorbis, WMA (Windows Media Audio), AAC and VQF compression at different levels to see the differences. The sample used corresponds to a rock song of 1:47 minutes, which includes various sections of solo instruments (programmed beats, guitars, piano), together with sections of instruments together, with enough use of cymbals (hi-hat and ride).
For the different formats were used the following programs:
Understanding that audio perception is highly subjective and that the opinion of other people might be different, I present the preliminary results:
96 kbps
This rate is one of the lowest that can be used if it is to have a relatively good quality of listening.
For a file of 17Mb (1:43 seconds) rock music, I had the following encoding time and file size:
Mp3 1:05 1,17 Mb
VQF 2 minutes 1,17 Mb
15 seconds 1.19 Mb WMA
AAC 2:17 minutes 1, 18 Mb
Ogg Vorbis 1 minutes 1,39 Mb
Ogg Vorbis has the distinction of being, preferably, of fixed over variable bitrate, so that even if its set to 96 kbps rate, tends to occupy a little more in those passages where required.
As we see, the faster the WMA encoder, then Vorbis, followed by the MP3, VQF and the slower the AAC.
As for audio quality, by far the worst was to Mp3. Apart from reducing the total sampling frequency of 44.1 KHz to 32 KHz and extend the treble, you hear many artifacts at all frequencies, especially in the acute (cymbal) – the familiar ‘glitch-glitch’ licuoso, along with distortions in the stereo field, and emergence of specific frequencies in parts of the field where it should be.
For VQF, it tends to do a little better because there are no artifacts so strong, medium and low tones sound good, although quite sharp lengthen – the hi-hat sound like tambourines, without distorting both as artifacts Mp3 with “glitch”, the stereo field remains quite faithful.
WMA has a somewhat inferior quality to VQF, as in a section where a hi-hat sequence very short (type 808), produced small cuts in the sound and produces artifacts similar to those of Mp3 in the rides, although less force, also produced distortions in the stereo field.
With Vorbis, somewhat elongate acute, but not in the VQF as the rest of the frequencies are quite faithful, though the treble sounds a bit brighter than the originals. There are no significant effects of tremolo.
AAC tends to produce a more or less than the Vorbis glitch in certain sections, although the difference is very small. Appears less artificial brightness in Vorbis, but more distortion in the mids.
Personally, the quality order is as follows: Vorbis and AAC (little difference, although AAC is smaller), VQF, WMA and Mp3.
128 kbps
This rate is the most used Mp3 compression, so I pay special attention.
VQF format and can not be filled at this rate, since the maximum compression rate is 44 kbps per channel (98 kbps in stereo).
The results of coding are as follows
Mp3 30 seconds 1,57 Mb
WMA 20 seconds 1,58 Mb
2:40 seconds AAC 1,57 Mb
Ogg Vorbis 1:40 minutes 1.56 Mb
As shown, the encoding time for the Mp3 is drastically reduced, probably because no need for conversion from 44.1 KHz to 34 KHz. In the case of Vorbis, compression time increases slightly compared with the minute and a half to 96 Kbps WMA encoding time is still amazing (20 seconds!), While the PCA remains the slower decline speed somewhat.
File sizes
Regarding the file size, the four formats occupy almost the same size, although the Vorbis occupies a little less, because of its use of variable compression rate for the less complex sections (silence).
Quality
In summary, the formats are ordered in the following order: AAC and Vorbis (barely), WMA and Mp3.
CCT tended to increase the separation of some sections and add a little glitch (almost imperceptible) to the dishes. Vorbis does equally well, but adds a little glitch and glamor of the treble. It is difficult to perceive the difference.
WMA had more problems, specifically in the areas where there was a solo instrument. First, has the typical effect of lengthening the acute VQF, making the hi-hat solo sound like tambourines; worst behaved with a line of hi-hat type 808, as it produced a lot of distortion in the stereo field, along with a noticeable tremolo (cuts in the sound). In sections with more instruments performed better, although it tended to lengthen as acute and produce in the rides sound like “Shhiii” only glitch.
With respect to Mp3, produces artifacts in the mids when sounded many instruments at once. It is also remarkable the effect of “glitch” with the hi-hat type 808 and the rest of the dishes sound a little glitch and more original brightness. It also presents stereo distortion of the field, when one channel has much less volume than the other.
