MPWG stands for MPEG video compression standard, and MPEG audio file refers to the sound part of MPEG standard, namely MPEG audio layer. According to the different compression quality and coding complexity, MPEG audio files can be divided into three layers (MPEG audio layers are 1/2/3 and MP 1 respectively. MP2 and MP3 have high compression rates corresponding to MPEG audio coding. The compression rates of MP 1 and MP2 are 4: 1 and 6: 1-8: 1 respectively, while the compression rate of MP3 is as high as10:12. That is to say, one minute of CD-quality music needs 10MB storage space without compression, while MP3 compression and coding only needs about 10MB, and the sound quality remains basically undistorted. So MP3 is the most common music format on the Internet at present. In order to reduce the sound distortion, MP3 adopts a coding algorithm called "sensory coding technology": firstly, the audio file is analyzed in frequency spectrum, then the noise level is reduced by a filter, and then each bit left is quantized and scattered, finally an MP3 file with high compression ratio is formed, and the compressed file can achieve the sound effect close to the original sound source when playing back. Although it is lossy compression, its biggest advantage is that a very small sound distortion can produce a high compression ratio.
MP4:
Shortly after MP3 came out, it opened up a brand-new music field with its high compression ratio of 12: 1 and good sound quality. However, the openness of MP[3] inevitably leads to copyright disputes. In this context, MP4 with smaller files, better sound quality and more effective copyright protection came into being. There is no necessary connection between MP3 and MP4. First of all, MP3 is an international technical standard for audio compression, and MP4 is indeed a brand name. Secondly, the audio compression technology he uses is also very different. MP4 uses a2b music compression technology developed by AT&T Company, and perceptual coding is the key technology. The compression ratio has been successfully increased to 15: 1, and the maximum compression ratio can reach 20. 1 without affecting the actual listening sense of music. At the same time, mp4 is specially designed in encryption and authorization, which has the following characteristics:
Each mp4 song is an extension. exe。 It is very convenient to double-click to run and play in windows. At the same time, Mp4 has some congenital defects-it is easy to be infected with computer viruses!
Smaller! Better sound quality? I want to adopt advanced a2b audio compression technology, so that the mp4 file size is only about three-quarters of that of mp3. From this point of view, np4 is more suitable to spread on inter, and it is said that the sound quality is better, but I have never heard of anything superior to mp3.
Unique digital watermark. Mp4 adopted the digital watermarking technology named "SOLANA" in April. It is convenient to track and discover pirated distribution behavior. In addition, any illegal decompression of mp4 may lead to the destruction of mp4 original files.
Support copyright protection. Mp4 music also has built-in copyright descriptions including words and images related to the copyright owner of the work, which can explain the copyright. This is also a respect for the author and singer.
The function is more perfect. Np4 can independently adjust the volume control of the left and right channels, and the built-in waveform/frequency division dynamic audio display and music manager can support a variety of color images, website connection and infinite scrolling text display.