MP3:
The full name of MP3 is Audio Layer III of Moving Picture Experts Group. This is a popular digital audio coding and lossy compression format. It aims to greatly reduce the amount of audio data, but for most users, the sound quality of playback has not decreased significantly compared with the original uncompressed audio. It was invented and standardized in 199 1 by a group of engineers from Fraunhofer-Gesellschaft in Hellem.
Simply put, MP3 is an audio compression technology. Because the full name of this compression method is MPEG Audio Layer3, people call it MP3 for short. MP3 uses the technology of MPEG Audio Layer 3, and compresses music into files with smaller capacity with the compression ratio of 1: 12 or even1:12. In other words, it can compress files to a smaller extent without losing sound quality. But also the original sound quality is well maintained. Because of its small size and high sound quality, MP3 format has almost become synonymous with online music. The MP3 format of music per minute is only about 1MB, so the size of each song is only 3-4MB. Use MP3 player to decompress (decode) MP3 files in real time, thus playing high-quality MP3 music. MP3 is a data compression format. It discards the data that is not important to human hearing in PCM audio data (similar to JPEG, which is a lossy image compression), thus achieving a smaller file size. Many techniques are used in MP3, including psychoacoustics, to determine which part of audio can be discarded. MP3 audio can be compressed at different bit rates, which provides a series of compromises between data size and sound quality. According to the MPEG specification, AAC (Advanced Audio Coding) in MPEG-4 will be the next generation MP3 format, although there are many important efforts to create and popularize other formats. However, due to the unprecedented popularity of MP3, the success of any other format is unlikely at present. MP3 has not only extensive client software support, but also many hardware support, such as portable media player (MP3 player) DVD and CD player. MP3 is different from DVD. MP3 players are all composed of two or more circuit boards, which are mostly connected by inserts. After long-term use, this plug-in may be in poor contact, resulting in various failures, and it can't be turned on at all in serious cases. Of course, such problems are generally relatively simple to maintain. You can unplug the plug-in directly, and then wash it with a brush dipped in anhydrous alcohol. After repeated cleaning several times, the poor contact of the contact can be removed. If it still doesn't work, it can be sold to electronic recycling enterprises for environmental protection.
Format characteristics:
1.MP3 is a data compression format. 2. It discards the data that is not important to human hearing in PCM audio data (similar to JPEG, which is a lossy image compression), thus achieving a smaller file size. 3.MP3 audio can be compressed at different bit rates, which provides a series of trade-offs between data size and sound quality. MP3 format uses hybrid conversion mechanism to convert time domain signals into frequency domain signals. 4.32 band polyphase integral filter (PQF). 5.36 or 12 tap modified discrete cosine filter (MDCT); The size of each sub-band can be 0... 1 and 2...3 1.6.MP3 not only has extensive client software support, but also many hardware supports, such as portable media players (MP3 players) DVD and CD players.
wmv:
WMV is a streaming media format introduced by Microsoft, which is an upgrade and extension of ASF (Advanced Streaming Format) format. Under the same video quality, WMV format is very small, which is very suitable for playing and transmitting on the Internet. AVI file encapsulates video and audio in one file, and allows audio and video playback to be synchronized. Similar to DVD video format, AVI files support multiple video streams and audio streams.
WMV is a streaming media format introduced by Microsoft, which is an upgrade and extension of ASF(AdvancedStreamFormat) format. Under the same video quality, WMV format files can be downloaded and played at the same time, which is very suitable for playing and transmitting on the Internet. WMV is not only developed based on Microsoft's own technology. Since the seventh edition (WMV 1), Microsoft has started to use its own non-standard MPEG-4Part2. However, the ninth edition of WMV is an independent standard of SMPTE (42 1M, also known as VC- 1), so the development of WMV is not a proprietary codec technology like MPEG-4. At present, there are 16 companies enjoying the patent of VC-1(April 2006), and Microsoft is also one of the companies enjoying the patent of MPEG-4 AVC/H.264. Microsoft's WMV is still very influential. However, due to Microsoft's own limitations, its WMV application development is not smooth. First, WM9 is a product of Microsoft and must rely on Windows. Windows means that the decoding part should also have a PC, at least the motherboard of the PC. This increases the cost of set-top boxes, thus affecting the popularity of video on demand. Second, the video transmission delay of WMV technology is 10 second. Wmv-HD is one of Wmv, which is a video compression format created by Microsoft, a software giant. WMV as a file suffix. Its compression ratio can be higher than MPEG-2 standard, and it is also a 2-hour HDTV program. If MPEG-2 is used, it can only be compressed to 30GB at most, while if a high compression rate encoder such as WMV-HD is used, it can be compressed to less than 15GB, and the image quality is not degraded. WMV-HD based on WMV9 standard is a version of the video compression technology series developed by Microsoft. Although WMV-HD is a unique standard of Microsoft, it is rapidly popularized in desktop systems because it strongly supports WMV series versions in the operating system. In terms of performance, the data compression ratio of wmv-HD is the same as that of H.264, and their application fields are also very similar. Generally speaking, HDTV files use. The WMV suffix is compressed by WMV HD.
WMV is not only developed based on Microsoft's own technology. Since the seventh edition (WMV 1), Microsoft has started to use its own non-standard MPEG-4 Part 2. However, since the ninth edition of WMV is already an independent standard of MPTE (42 1M, also known as VC- 1), it is reasonable to believe that the development of WMV is not a proprietary codec technology like MPEG-4.
At present, there are 16 companies enjoying the patent of VC-1(April 2006), and Microsoft is also one of the companies enjoying the patent of MPEG-4 AVC/H.264. Microsoft's WMV is still very influential. However, due to Microsoft's own limitations, its WMV application development is not smooth. First, WM9 is a product of Microsoft and must rely on Windows. Windows means that the decoding part should also have a PC, at least the motherboard of the PC. This greatly increases the cost of set-top boxes, thus affecting the popularity of video on demand. Secondly, the video transmission delay of WMV technology is very large, usually 10 second. Because of this restriction, WMV can only browse WM9 video files on the computer at present. Wmv-HD is a video compression format created by Microsoft, a software giant, and is generally adopted. WMV as a file suffix. Its compression ratio is even higher than MPEG-2 standard, and it is also a 2-hour HDTV program. If MPEG-2 is used, it can only be compressed to 30GB at most, while if a high compression rate encoder such as WMV-HD is used, it can be compressed to less than 15GB, and the image quality is not degraded. Based on WMV9 standard, WMV-HD is the latest version of video compression technology series developed by Microsoft. Although WMV-HD is a unique standard of Microsoft, it is rapidly popularized in desktop systems because it strongly supports WMV series versions in the operating system. In terms of performance, the data compression ratio of WMV-HD is the same as that of H.264, and its application fields are also very similar. Therefore, in the struggle for the dominance of the new generation of mainstream video coding standards, the two sides launched a tit-for-tat struggle, focusing on the next generation of optical disc specification "HD DVD" and digital microwave broadcasting and television. Generally speaking, HDTV files use. The wmv suffix is compressed by WMV-HD. At present, the DVD Forum has preliminarily approved Microsoft's MPEG-2, H.264 and WMA-HD as the mandatory standards of the next generation DVD, namely HD-DVD technology. WMV files usually contain video and audio parts. The video part is encoded by Windows Media Video, and the audio part is encoded by Windows Media Audio. Recently, WMV files have been resisted by some users, mainly because WMV video files often need IE download license and certificate to watch. Trojan horse virus makers often use this point to bind the process of popping up viruses and downloading certificates, which brings inconvenience and threats to users. Many advertisers and even busybodies also take the opportunity to plant their own advertising windows to increase traffic. We input DRV pop-ups and WMV pop-ups into search engines, and we can find that many websites have special pop-up tools to download, which makes users in WMV and WMA formats fall into a helpless situation, because at present, the pop-ups of RM and RMVB can be simply restricted and shielded, while the embedded pop-ups of DRV used by WMV are difficult to clear. However, no matter whether this format is safe or not, there will always be people who indulge in it for the sake of harming others and benefiting themselves, even if it seems to be safe at present.