So called nondestructiveCompressed format, is the use of data statisticsredundancyCompression can completely recover the original data without causing any distortion, butcompression ratioIt is limited by the theory of statistical redundancy of data, generally 2:1 to 5:1. Such methods are widely used in text data, programs and special applicationsimageData (e.gfingerprintImage, medical image, etc.).
Due to the limitation of compression ratio, it is impossible to solve the problem only by using lossless compression methodimageanddigital video The lossless compression methods commonly used include Shannon Fano coding, Huffman coding, Run length coding, LZW (Lempel Ziv Welch) coding andarithmetic coding Etc.
So called nondestructiveCompressed formatAs its name implies, it compresses the sound signal without lossaudio frequencyFormat.Common imagesMP3、WMAAnd other formats areLossy compressionFormat. Compared with the source WAV file, they all have a considerable degree of signal loss, which is 10%compression ratioThe root cause of.Without damageCompressed format, just like compression with Zip or RARSoftwareDecompressionsound signal, the compressed format is restored to a WAV file, which is exactly the same as the WAV file as the source!But if you use Zip or RAR to compress the WAV file, you mustCompressed packageIt can only be played after decompression.The lossless compression format can be played directlySoftwareRealize real-time playback, which is the same as MP3 and other lossy formats.In a word, lossless compression format can be used without sacrificing anysound signalOn the premise of reducing the volume of WAV files.
Advantages and disadvantages
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advantage
1. 100% saved without any signal loss
lossless compression
As mentioned before, lossless compression format is like using ZipCompressed fileSimilarly, we can 100% save all data of WAV files, which can be proved by the "WAV comparison" function of EAC.One of U2's "Beautiful Day"Grab railSave it in WAV format as our original file.Set this WAVFile compressionbecomeAPE format, and then the APE filedecompression In WAV format.Use the "WAV Compare" function of EAC to compare the data between the two WAV files. The result is shown in Figure 1. EAC does not report any inconsistency!If the WAV file is compressed into MP3 and then decompressed, it is inconsistent from beginning to end compared with the original WAV file!Many friends want to copy the CD "original" to the hard disk as much as possible, and at the same time, they want to reduce the space consumption. In the past, it seems that only 320Kbps CBRMP3 is the solution, but that is far from 100%!The emergence of lossless compression format provides an almost perfect solutionprogramme。
2. High sound quality, not affected bysignal sourceImpact of
Since it is 100% originalsound signalThe sound quality of lossless compression format is undoubtedly the same as that of the original CD!Compare the WAV format of Beautiful Day with the spectrum of the FLAC compressed format. Can you see any difference?Similarly, the actual listening cannot be any different!andLossy compressionBecause of its innate design (some signals need to be lost), the sound quality can only be infinitely close to the original CD, and it is impossible to really reach the CD level!Moreover, due to the limitations of lossy compression format algorithm, when compressing symphony and other types of music with large dynamic range, its sound quality performance is unsatisfactory.The lossless compression format does not have such a problem, and any music type is all right!
3. Convenient conversion
Lossless compression format can be easily restored to WAV, and can also be directly converted to MP3, Ogg, etcLossy compressionFormat, and can even convert between different lossless compression formats without losing any data.This is much better than lossy format!Because of the secondary encoding of the lossy compression format (converting from one lossy format to another, or adjusting the format without changing itBit rate）It means that more signals are lost and more distortion is brought!
Insufficient
1. Large space consumption, low compression ratio
Compared with lossy compression format, lossless compression format has a much lower compression capacity, generally around 60%.The 192Kbps lossy format is only about 14% of the original filecompression ratioThe difference is quite wide.As shown in Figure 5, a U2 Beautiful Day is compressed in different formats, including APE in Normal mode and La in High mode.However, it can be seen that the data is also 100% saved, and the compression capacity of lossless format is better than that of specialMulti-MediaRAR with optimized format should be strong, while Zip can hardly compress WAV format.In addition, the lossless format has the real-time playback capability that RAR and Zip do not have. We still have the same technology for lossless formatadmireOf!
2. Lack of hardware support
FLAC formatOnly a few hardware support[1]But Sony's atrac advanced lossless is in SonyWalkmanThere is broad support in.Besides Karma, Sony nw-x1000 series, nw-a840 series and nw-s740 series can play walkman in lossless compression format.The capacity of mainstream flash MP3 walkman has reached 4GB to 16GB.However, few people know about lossless format, and few people are willing to spend time on downloading music. The market demand is small, and the supply is naturally small, so the development of walkman is slow, and the support for lossless music is less.
Lossless format
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Well known lossless compression formats include APE and FLAC[2], TAK, WavPack, TTA, etc.
AAL
ATRAC Advanced Lossless is an ATRAC format developed by Sony CorporATIon.By combining ATRAC3 or ATRAC3plusaudio frequencycompression technique And the latest lossless compression algorithm, while maintaining the playback compatibility with traditional devices, perfectly realizes the lossless compression of data with a very low data size.Referred to as AAL files, some HI-MD products can support AAL files through upgrading.
The AAL file is divided into two parts. One part is 256k A3plus, which can also be other A3 or A3+, and the other part is music details. So for ordinary Sony Walkman, there is only 256K playback.Only the machines that really support AAL can play other details.
APE
APE(Monkey's Audio) is undoubtedly a very famous lossless compression format, which has been widely used in China.itscompression ratioIt is excellent, efficient and fast, and its comprehensive ability is definitely among the best today.Through BT orEmule You can download a lot of music in APE format.And the widely used Monkey's Audio production software has also greatly promoted the popularity of this format.However, APE also has many shortcomings. Its decoding speed is not ideal, and it requires high CPU computing power. It can only be used on the Windows platform. Any data corruption will lead to the scrapping of the entire file.In addition, although APE provides freesource code, but it is not an open source agreement, which has limited the improvement, so the APE format is on the decline, and some European and American music forums have abandoned the format.
FLAC
FlAC(FreeLosslessAudioCodec) is a very mature lossless compression format. The source code of this format is completely open and compatible with almost alloperating systemPlatform.Its coding algorithm is quite mature, has passed strict tests, and is said to play normally even if the file point is damaged (the damaged part is replaced by mute).This format is not only supported by mature Windows production programs, but also by many third-party software.In addition, this format is the only lossless format that has been supported by hardware. Karma of Rio's hard disk walkman, and Jianwu'sCar audio MusicKeg and PhatBox's digital players can support FLAC format.
WavPack
Lossless compressed file
The format is quite distinctive and worth a try.WavPack is not only a lossless compression format, but also aLossy compressionFormat.In its unique "hybrid" mode, WavPack can be compressed into a combination of wv files (lossy compression format, the size is generally equivalent to about 23% of WAV files)+wvc files (modified files, the size is generally equivalent to about 41% of WAV files).With the corresponding wvc file, the lossy compression format of the wv file becomes a lossless format, which is exactly the same as the ordinary lossless compression format when playing.If you want to reduce the file size, you can remove the wvc file. At this time, the wv file will become a lossy format. It will play exactly like the high bit rate MP3!WavPack contains both lossless and lossy formats. Isn't it amazing?Through the WavPackFrontend foreground program, we can easily use the WavPack format.
LPAC
In the lossless format of the mid track mid moment, all indicators are relatively average.The author Tilman Liebchen has prepared a good production program for it, but has stopped updating independently, and it is a standard of MPEG4.
WMALossless
MicrosoftLossless compression is also available after Windows Media Player 9.0.Just click the menu "Tools"="Options" and select "WindowsMedia" in the "Copy Music" tabaudio frequencyLossless "format.In the future, through the "Copy from CD" function of WMP, you can directly save the CD to WMALossless format, which is really very convenient to use.But apart from Windows Media Player, there are few othersSoftwareThis format can be supported.
AppleLossless
The latest version of Apple iTunes musicSoftwareApple Lossless lossless compression format is also provided in.Like Windows Media Player, iTunes can quickly grab tracks from CDs and compress them into AppleLossless format.Of course, this format is also only supported by your own software.
La
La，LosslessAudio is short for LosslessAudio. Although the format is not famous, it is the champion of compression ratio,compression ratioNo one can compete, including APE, which is always famous for its high compression rate!Because the compression is too strong, its encoding and decoding speed is slow enough, and the software supporting it is relatively small.Only Winamp decoding developed by ourselvesplug-in unitAnd the coder LosslessAudioCompressor of Windows interface.
OptimFROG
The compression rate of this format is comparable to La, but the speed is slower than La.
Shorten
It is a lossless format with very fast encoding speed, but the compression rate is disappointing!This format is also open source, and supports both Windows and Mac. However, it has not updated the encoding version for a long time, and it is estimated to have died.
Lossless compression formats are far more than the above, including RKAU, SZIP, Bonk, Kexis, etc. Since they are very rare and imperfect, they will not be introduced.
Kenwood
Kenwood's original lossless compression method records the content of high-quality music CDs, which can be used more effectivelyHard disk storageIt can store more data (the average compression rate is 60%), and can also effectively restore the compressed files to the original state, so that high-quality sound quality can be guaranteed.
TAK
TAK (Tom's Audio Kompressor) is a new typeLossless audioCompressed format, full name is Tom's Audio Kompressor, produced inGermany, the prevalence is rising.Not open source, but the author said that he would open source at an appropriate time.The latest version is 2.0, and TAK compressed by the higher version can no longer be recognized by the lower version.It is similar to FLAC and APE. In general, the compression ratio is similar to APE anddecompression The speed is similar to that of FLAC, which is a combination of the advantages of both.In addition, the encoder compressed with this formataudio frequencyIf it is VBR, it can be changedBit rateOf.
Several features:
-Excellent compression ratio.The compression ratio using the Extra parameter is similar to the High parameter of APE, while the result using the Turbo parameter, the fastest compression parameter of TAK, is comparable to the effect of the parameter with the highest compression ratio of FLAC.
-Faster compression speed.The author said that under the same compression rate, he knew that no other format could compress the parameters faster than the Turbo and Fast of TAK.
-Stream support.Every two seconds, a frame containing all the information needed for decoding will be inserted into theaudio frequencyMedium.
-Fault tolerance.1 bit information error, affecting up to 250 millisecondsaudio frequency。Due to the technical support mentioned above, the compression using this format is seriously damagedaudio frequencyIt can also be played as usual, at the cost that the damaged part is replaced by mute.
-Error checking.24 bit CRC check is used for each frame.
-Simple and fast search capability.That is, when you need to play from a certain point in the middle, you can quickly find the place you want to start playing, and the positioning is also very accurate.
TTA (True Audio) is a free and simple real-timeLossless audioCodec, but popularity is declining.TTA is a lossless audio compression based on adaptive prediction filtering. Compared with other main formats, TTA can have the same or better compression level while maintaining a higher speed.
TTA losslessAudio codingThe characteristics of are:
First, the compression ratio can reach 10:3;Second, real-time coding;Third, free and opensource codeAnd documents;Fourth, different platforms can be compiled;Fifth, simple and convenient data format;Sixth, it can be used as variousmusic player Input ofplug-in unit；Seventh, provide Windows users withgraphical user interface（ GUI ）；Eighth, DirectShow technical support.
TTA lossless audio codec canaudio frequencyThe file is compressed.This compression results in no loss of data or quality;And whendecompression After the source audio fileData bitsSame.The different compression ratios achieved by the TTA decoder depend on the music type, but range from 30% to 70%.TTA lossless compressionAudio formatSupport ID3v1 and ID3v2 label information.
TTALossless audioCodec, which can store music of up to 20 audio CDs, is equivalent to a single DVD - R, and retains the originalCD sound qualityAnd details of the popular ID3 tag format.
Although there are still some shortcomings, the prospect of lossless compression format is undoubtedly bright, as can be seen from the number of existing lossless compression formats!As time goes by, various factors limiting lossless format will be eliminated gradually!For example, with the continuous increase of hard disk capacity, 1TB mechanical hard disk has become the mainstream, 200GB solid state disk will also be popular, and the problem of large space occupied by lossless format will no longer be a problem.And faster decoding chips will also be developed. I believe there will be more and more hard disksWalkmanSupport lossless format.In the near future, when the capacity of the flash walkman is calculated in terabytes, the lossless compression format will be paid more and more attention to in pursuit of higher sound quality!
TAC
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As a leading music service platform in China, TAC music in lossless format, MP3, etcLossy compressionDifferent ways, tac istencentA lossless audio compression technology that is encrypted on the basis of FLAC. Its essence is a modified FLAC format. Like other lossless formats, it can ensure no loss of sound quality.Due to the closed encryption method, this format can ensure that the achievements of the music copyright owner will not be pirated or embezzled, and that the music can only be played on QQ players, not copied to any unauthorized players.As long as users of Green Diamond select high-quality music to download from the music library, select "Lossless Audio Quality" in the "Select Audio Quality" section of the download page, and click "Start Download", users can easily collect unlimited good music.
