Audio (audio) compression comparison [mp3, wma, ogg, atrac] Part 2


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Audio (audio) compression comparison [mp3, wma, ogg, atrac] Part 2

AUDIO COMPRESSION

[Sound source used and points of interest]
・ 1kHz sine wave
Check for noise or correction. Investigate if abnormal sounds are mixed by emphasis or noise different from the originally generated range.

Audio Compression

· White noise
Check the frequency characteristics. Use sounds that are emitted at the same level for all sounds from 0 to 20 kHz and see if they are reproduced correctly.

·music
Use real music and investigate the differences with the original.

[Bitrate Settings]
Fixed bit rate: 96kHz, 128kHz, 256kHz, 320kHz Variable bit rate: 96-160kHz, 192-320kHz.
However, depending on the software, 320kHz cannot be set fixed and 350 can be set, or the upper and lower limit bits cannot be specified in the variable, and the sound quality standard can be specified in several steps ( medium sound quality, high sound quality). quality).be. Also, there are some that are configured with average bitrate instead of variable bitrate, so understand that it’s not a completely fair comparison.

[Software used [encoder]]
・ MP3 system
Afternoon Koda Ver.3.11a [gogo.exe ver.3.11]
Lame Ivy Frontend Encoder Ver.2.91 [Lame.exe Ver.3.93]
B’s GOLD Ver.7.12 [Unknown]
RipAudiCO Ver.3.70 [leme_enc.dll Ver.3.93]

・OGG system
oggdropXPd Ver.1.7.11 [Unknown]
B’s GOLD Ver.7.12 [Unknown]

・ WMA
B’s GOLD Ver.7.12 [Unknown]
(For WMA, I tried 3 types of software in my environment, but the result was exactly the same (maybe the encoder itself uses the same thing?) And it corresponds by software Since the bitrate range was narrow, only used a type).

・ ATRAC
nothing special. For ATRAC, we recorded analog from a CD player to an MD deck, optically connected an MD deck to a PC, and measured what was captured by WAV.

· To measure
Wave Space Ver.1.31

【others】
Although it is different from the main theme, I converted it to WAV for the visual measurement of each standard (because WaveSpace only supports wav), but the position where the sound of the WAVized data ends and the total playback. We discovered that there was a difference in time. , so we also investigated it.

3.Hardware 3.
Originally, the equipment used should be described in detail here, but the hardware environment is different for each individual, and this survey is only a guide in the first place, and it will be different if other people do the same. is a possibility of results, I will omit the detailed description of the hardware. (The thing is that I don’t have enough equipment to publish)

【Results of the test】
See the following for a summary of the results of each survey.
・White noise measurement result
・1kHz sine wave measurement result
・Music measurement results
・Simple file size and comment list

[Discussion]
ah There seems to be no big difference in file size (between the same bitrate)
stomach. Sound quality appears to be MP3 < WMA < OGG at low bit rates
(MP3: 128 = WMA: 96 < OGG: 96).
Hare. There is little difference at high bit rates
(there is a slight difference in the treble range, but it seems you won’t notice the difference unless you’re in a very good environment).
Worker. The difference in the encoder software was more than I expected
(especially in MP3)

“My conclusion”
[Less than 128]
If you’re worried about popularization (compatibility), [WMA] is good, and if you basically use it alone, [OGG] is good.
(I am worried about the amount of noise or the correction, but I sacrificed a bit on the sound quality anyway, so I chose the one that covers up to the high range as it is. Also, due to the relationship between ① and ②, mp3 is another with the same sound quality.The file size will be larger than

[With 256 and more]
The variable bit rate (192-320) of [Afternoon Koda] is good.
The fixed 320 is good for sound quality, but there is little difference between the fixed 256 and variable high-quality sound, and it seems that you can barely understand it even if you listen to it. If the sound quality is about the same, the smaller the file size, the better.

[Other impressions]
About OGG
I had high expectations for OGG, but I was concerned about the measurement result at 1 kHz, whether it was noise or correction. However, I find the relationship between sound quality (wide playback band) at low bit rates and file size to be excellent. At high bit rates the sound quality and file size are about the same as MP3s so I think MP3s are advantageous considering the penetration rate but I think they are doing pretty well considering the fact that they have just been developed. expected in the future


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Audio (audio) compression comparison [mp3, wma, ogg, atrac]

Audio (audio) compression comparison [mp3, wma, ogg, atrac]

Compressed Audio

MP3-typed audio, etc., for storing music that was recorded on cassette tapes, music borrowed from CD rental shops or purchased music CDs, or for easy enjoyment with a portable player or car.

compressed audio

More and more people are recording with compression technology. However, there are many standards such as WMA recommended by Microsoft as well as MP3 when it comes to audio compression. Also, since the sound quality and compression rate of each standard change depending on the bit rate setting and the like, there is a wide variety of compression methods depending on the combination of the standard and the setting.

So, I wanted to check what the sound quality and file size would be when recording with which standard and with which settings, and select the standard that suits my purpose, so I took this survey. However, due to the investigation of the ideas of fans, the software and equipment used were covered by those that are freely obtainable in hand or on the net, so the result may be different from the original performance. , but it is only one. Take it as an example.
Since this test focuses on sound quality, it does not test at a low bit rate, which deteriorates sound quality.

Finally, in conducting this survey, I referenced many documents on the Internet. We would like to express our gratitude to each person (individual/corporation) for facilitating us to review materials that have been researched and created with considerable effort from their respective points of view. The sites I mainly referred to will be featured at the bottom of this page, so I recommend that those who are viewing this also take a look.

[Survey outline]
1. 1. Destination standards
As mentioned above, there are many audio compression standards, but here we have limited them to MP3, WMA, OGG, and ATRAC. The standards and reasons for the survey are shown below.

・MP3 ( Moving Picture Experts Group 1 Audio Layer – 3 )
I chose it because it is probably the best known and most popular standard and there are many compatible players for the same reason.

・WMA ( Windows Media Audio ) _ _
It is widely known alongside MP3. Recently, it has become compatible with car audio and DVD players. Also, according to a theory, the same bitrate is rumored to have higher sound quality and compression than MP3, so I chose it.

・OGG (Ogg Vorbis)
It may not be familiar to you yet, but although MP3 requires a license, the number of compatible players is gradually increasing due to the fact that it is unlicensed but offers high sound quality and high compression. Since it is (apparently) high-performance and license-free, it is easy to develop encoders and playback software, so we chose it with the expectation that it will spread in the future.

・ATRAC ( Advanced TR Transform Acoustic Coding ) _ _
This name may not be familiar to you, but you can understand the standard adopted by MD. Many people think that MD has the same high sound quality as CD, and since it is widely used as a storage medium for music, it was used as a reference for comparison.

・ Reason for not targeting other standards
There are many compression standards in addition to the above, but there are few compatible software and players, and considering the interaction with others (although I cannot say publicly), I judged that the comparison with the three types above is adequate. In addition, there is a standard called OpenMG (ATRAC3) recommended by SONY, etc., and there is no need to adopt other than SONY in mobile players, etc., but there are still few (limited) supported players, and recording is done. except for VAIO users, since it is difficult to do so, it was excluded from the target.

2. 2. Survey method
The three types of sounds selected for the survey were converted to various bit rates of each standard, visually compared to the original sounds, and listened to and evaluated. Also, I heard rumors that although the standard is the same, there are differences depending on the conversion software, so I used various types of software (encoder). the detail is just below.

Compressed audio formats

Compressed audio formats

Compressed Audio File Formats

Understanding compressed audio formats
The digital age dictates its own laws, according to which, in particular, audio and video information is more convenient to store and transmit in compressed form. Let’s briefly discuss the principle of sound compression.

Compressed Audio file formats

As you know, the music we listen to consists of a set of signals, each of which has its own characteristics, including loudness. The human auditory system is designed so that we do not distinguish or misdirect a weak (low) signal from the background of a strong (strong) signal. This principle forms the basis of modern means of compression (compression) of audio data.

If we imagine that a signal of a certain length is divided into many parts, and each part is processed in such a way that a weaker signal, which is difficult to distinguish from a strong one, falls under the knife and a stronger signal remains, then this will be a rough model of audio signal compression. … Consequently, the level of data compression will depend on how many parts (samples) the original file will be divided into and how many weak signals from each individual sample will be removed (what the bit rate will be: the number of bits in a sample of a specified duration).

The first versions of codecs for data compression acted quite crudely: they just cut off a weak signal and did not take into account the type of music, therefore, rather energetic music, without special nuances, in a compressed form does not it sounded worse than the original, whereas more complex classical and acoustic music simply lost all color and depth.

As a result of this, a transition to a more intelligent compression algorithm, with a variable bit rate, was made. Depending on the musical texture, that is, the ratio of weak and strong signals, the codec changes the amount of weak signals cut, so that we hear a more believable sound.

Obviously, with a higher sample rate (sampling) of 44.1-48.0 KHz and a higher bit rate (160-192 Kbps), we will get a sound more consistent with the original than with a sample rate 22 KHz and 64 Kbps bit rate. However, the size of the final compressed file is directly proportional to the selected sample rate and bit rate, and this is what people who distribute music in the form of compressed (compressed).

It should also be remembered that most algorithms cut the upper part of the audible range as well, starting at around 15 kHz.

There are currently several original compression algorithms, most of which are compatible with Linux.

Ogg Vorbis
Ogg Vorbis is a completely open audio format that allows you to store and transmit audio information with high sound quality (44.1-48.0 kHz sample rate, 16+ bits, polyphony (multi-channel audio)) and bit rates ranging from 16 to 512 kbps per channel. The number of channels processed can be as high as 255. This allows Vorbis to be on par with MPEG-4 (AAC and TwinVQ), WMA and PAC audio, and clearly superior to MPEG-1 Layer 3 (MP3) audio. .

Ogg Vorbis is also a streaming format, allowing it to be used, for example, for Internet broadcasts, especially since this format is compatible with Icecast. The characteristics of the codec algorithm allow you to get the final file smaller than MP3 files of similar quality.

For the reproduction the console program ogg123 is used, to encode – oggenc; both have graphic housings. More details on both are in the following sections.

MP3
MP3 or MPEG-1 audio layer 3 is by far the most popular format for storing and transmitting compressed data. This format was developed by the Frauenhofer Institut, Germany. However, despite the ubiquity of the format, it should not be forgotten that the patent for MP3 encoding and decoding algorithms belongs to a single company, so the end user at any time may find themselves in a very disadvantageous environment, such as It has already happened with the developers of free MP3 data compression tools …. You can get details about the license conditions on the developers website.

WMA
The WMA format is a proprietary product of Microsoft. It failed to occupy a market segment comparable to MP3, but it has some popularity despite serious security concerns identified. At the moment, only the universal MPlayer player can play WMA files. There are no free data compression tools for this algorithm and its appearance is unlikely.