In principle, there is no best, but the encoding or compression format is different. Generally speaking:

1. PCM coding

PCM Pulse Code Modulation is Pulse Code Abbreviation for Modulation. In the previous text, we mentioned the general workflow of PCM. We do not need to care about the calculation method used in the final encoding of PCM. We only need to know the advantages and disadvantages of the PCM-encoded audio stream. The biggest advantage of PCM encoding is good sound quality, but the biggest disadvantage is large size. Our common Audio CD uses PCM encoding, and the capacity of a disc can only hold 72 minutes of music information.

2. WAVE

This is an ancient audio file format developed by Microsoft. WAV is a file format that conforms to the PIFF Resource Interchange File Format specification. All WAVs have a file header, which contains the encoding parameters of the audio stream. WAV has no hard and fast rules for encoding audio streams. In addition to PCM, almost all encodings that support the ACM specification can encode WAV audio streams. Many friends don't have this concept. Let's use AVI as an example, because AVI and WAV are very similar in file structure, but AVI only has one more video stream. There are many kinds of AVI that we are exposed to, so we often need to install some Decode to watch some AVI. DivX, which we are exposed to more, is a video encoding. AVI can use DivX encoding to compress the video stream. Of course, other methods can also be used. Encoding compression. Similarly, WAV can also use a variety of audio encodings to compress its audio stream. However, what we commonly see are WAVs whose audio streams are encoded by PCM. However, this does not mean that WAV can only use PCM encoding. MP3 encoding can also be used in WAV. , just like AVI, you can enjoy these WAVs as long as the corresponding Decode is installed.

Under the Windows platform, WAV based on PCM encoding is the best supported audio format, and all audio software can perfectly support it. Since it can meet higher sound quality requirements, WAV is also The preferred format for music editing and creation, suitable for saving music materials. Therefore, WAV based on PCM encoding is used as an intermediary format and is often used in the mutual conversion of other encodings, such as MP3 to WMA.

3. MP3 encoding

As the most popular audio compression format, MP3 is widely accepted by everyone. Various MP3-related software products emerge in endlessly, and more hardware products It has also begun to support MP3. Many VCD/DVD players we can buy can support MP3, and there are more portable MP3 players, etc. Although several major music dealers are extremely disgusted with this open format, they are also There is no way to prevent the survival and spread of this audio compression format. MP3 has been in development for 10 years. It is the abbreviation of MPEG (MPEG: Moving Picture Experts Group) Audio Layer-3. It is a derivative encoding scheme of MPEG1. It was successfully developed in 1993 by the German Fraunhofer IIS Research Institute and Thomson Company. MP3 can achieve an astonishing compression ratio of 12:1 while maintaining basically audible sound quality. In those days when hard drives were sky-high prices, MP3 was quickly accepted by users. With the popularity of the Internet, MP3 was accepted by hundreds of millions of users. MP3 encoding technology was actually very imperfect when it was released. Due to the lack of research on sound and human hearing, early MP3 encoders almost all encoded in a crude way, causing serious damage to the sound quality. With the continuous introduction of new technologies, mp3 encoding technology has been improved time and time again, including two major technical improvements.

VBR: MP3 format files have an interesting feature, that is, they can be read and played at the same time, which is also in line with the most basic characteristics of streaming media. In other words, the player can play the file without pre-reading the entire content of the file, and can play it wherever it is read, even if the file is partially damaged.

Although mp3 can have a file header, it is not very important for files in the mp3 format. Because of this characteristic, each segment and frame of the MP3 file can have a separate average data rate without the need for a special decoding scheme. So a technology called VBR (Variable Bitrate, Dynamic Data Rate) emerged, which allows each segment or even each frame of an MP3 file to have a separate bitrate. The advantage of this is that it can maximize sound quality while ensuring Limits the file size. The advantages of this technology are obvious, but it is indeed difficult to apply because it requires the encoder to know how to allocate bitrate to each segment. For encoders without waveform analysis, this technology is useless. Just like this, VBR technology did not appear dazzling as soon as it appeared.

1. FLC in the silent era

FLC and FLI are a video format developed by Autodesk. They only support 256 colors, but support color dithering technology, so they are very realistic in many cases. Color video is not very different and does not support audio signals. It seems that this format is useless now, but it was indeed the best and only choice in the DOS era without true color graphics cards and sound cards. The most important thing is that Autodesk's full range of animation production software provides support for this format, including the famous 3D Studio X, so this format represents the video encoding level of an era. To this day, there are still many video editing software that can read and generate this format. But after all, Lian Po is old, and this format has been ruthlessly eliminated.

2. Singing and dancing AVI

AVI——Audio Video Interleave, that is, audio and video interleave format. In early 1992, Microsoft launched AVI technology and its application software VFW (Video for Windows). In an AVI file, moving image and audio data are stored in an interleaved manner and are independent of the hardware device. This way of organizing audio and video data in an alternating manner makes it more efficient to obtain continuous information from the storage medium when reading the video data stream. The main parameters that make up an AVI file include video parameters, audio parameters and compression parameters. AVI files use the AVI RIFF format, and the AVI RIFF format is identified by the string "AVI". All AVI files include two required LIST blocks. These blocks define the format of the stream and data flow. AVI files may also include an index block.

As long as this standard is followed, any video encoding scheme can be used in AVI files. This means that AVI has very good scalability. Since this specification was formulated by Microsoft, Microsoft's full range of software, including programming tools VB and VC, provide the most direct support, thus further establishing AVI's video dominance on PCs. Due to the openness of AVI itself, it has received support from many coding technology developers. Different encodings have enabled AVI to be continuously improved. Now, almost all general video editing systems running on PCs mainly support AVI. The emergence of AVI announced the end of the era of dumb movies on PCs, and the continuously improving AVI format represents the rise of multimedia on PCs.

Speaking of AVI, we cannot but mention Intel's Indeo video series encoding. Indeo encoding technology is a high-performance, pure software video compression/decompression solution for PC video. Indeo audio software provides high-quality compressed audio for use on the Internet, intranets, and multimedia applications. It can perform both music and sound compression, with a compression ratio of up to 8:1 without significant loss of quality. Indeo technology can help you build richer multimedia websites. It is currently widely used for dynamic effect demonstrations, game cutscenes, non-linear material storage, etc. It is currently the most widely used AVI encoding technology. Now Indeo coding technology and related software products have been acquired by Ligos Technology. With the rise of MPEG, Indeo faces great challenges.

3. MPEG series encoding that takes into account both capacity and quality

Contrary to AVI, MPEG is not a simple file format, but an encoding scheme.

MPEG-1 (standard code name ISO/IEC11172) was formulated at the end of 1991. It deals with the standard interchange format (SIF) or source input format (Source Input Format, SIF). Multimedia streaming. It is an international standard for digital storage media moving images and their accompanying audio coding (MPEG-1 Audio, standard code ISO/IEC 11172-3) with a data transmission rate below 1.5Mbps. The audio standard was later derived into today's MP3 encoding scheme. MPEG-1 standardizes the traffic standards in PAL (352*288, 25 frames/S) and NTSC (352*240, 30 frames/S) modes, providing audio and video equivalent to a home video system (VHS). Quality, at this time the video data transmission rate is compressed to 1.15Mbps, and its video compression rate is 26:1. Using the MPEG-1 compression algorithm, a 120-minute long multimedia stream can be compressed to about 1.2GB in size. The common VCD is a masterpiece created by MPEG-1 encoding. MPEG-1 encoding does not necessarily have to operate according to the PAL/NTSC specification. You can freely set the image size and audio and video traffic. As the pickup accuracy of optical heads improved, some people increased the information density of optical discs and moderately reduced the audio stream flow rate. As a result, DVCDs emerged that could store one movie on just one optical disc. DVCD is actually an audio-visual product that has no industry standards, no national standards, let alone international standards.

When VCDs began to become popular in the market, computers just entered the 486 era. At that time, many friends dreamed of owning a hard decompression card to realize their long-cherished wish of watching VCDs on PC. Looking back today, , I thought it was a bit incredible, but the current situation at that time was that the 486 system could not play VCD smoothly without the help of hard decompression. MPEG-1, which even the tens of thousands of yuan 486 system could not play smoothly, was marked with the mark of nobility. With the release of Pentium, PCs began to take off. Later, Windows Media Player also directly provided support for MPEG-1. So far, MPEG-1 has been completely accessible on PCs.

MPEG-2 (standard code IOS/IEC13818) released the Draft International Standard (DIS) in 1994. The video coding algorithm is basically the same as MPEG-1, with some minor improvements, such as Added encoding for interlaced TV. What it pursues is higher-quality moving images and their accompanying sound effects under large traffic. The video quality of MPEG-2 is comparable to the broadcast quality of PAL or NTSC. In fact, MPEG-1 can also achieve similar effects. More improvements of MPEG-2 come from the encoding of the audio part. At present, the most common MPEG-2 related product is DVD, and SVCD also uses MPEG-2 encoding. MPEG-2 also has a more important use, which is to allow traditional televisions and television broadcasting systems to develop in the digital direction.

MPEG-3 was originally developed for HDTV. Due to the rapid development of MPEG-2, MPEG-3 was declared obsolete before it was completely completed.

MPEG-4 was announced in 1998. Unlike MPEG-2, MPEG-4 does not pursue high quality but high compression rate and interactive capabilities suitable for networks. MPEG-4 provides a very amazing compression rate. If VCD image quality is used as the standard, MPEG-4 can compress a 120-minute multimedia stream to 300M. The MPEG-4 standard is mainly used in video phone (Video Phone), video email (Video Email) and electronic news (Electronic News). Its transmission rate requirement is low, between 4800-64000 bits/sec, and the resolution is is 176X144. MPEG-4 uses a very narrow bandwidth to compress and transmit data through frame reconstruction technology in order to obtain the best image quality with the least data.

MJPEG is not specifically prepared for PCs, but is prepared for professional-level or even broadcast-level video capture and playback on the device, so MJPEG includes interlaced scanning optimized for traditional analog TV TV algorithm, if you play MJPEG encoded files on a PC, the effect will be ugly (if your graphics card does not support MJPEG motion compensation), but once output to the TV, you will immediately discover the benefits of this algorithm.

4. Streaming media belonging to the network

RealNetworks RealVideo uses the Real G2 Codec developed by RealNetworks itself. It has many advanced designs, such as SVT (Scalable Video Technology) ); Two-way encoding (Two-Encoding, similar to VBR). The audio part of RealMedia uses RealAudio, which can accept many audio encoding schemes and realize sound compression at different rates of mono and stereo music. The latest RealAudio actually uses the ATRAC3 encoding scheme to challenge the increasingly mature MP3.

Windows Media, video encoding uses the very advanced MPEG-4 video compression technology, called Microsoft MPEG-4 Video Codec, and audio encoding uses a coding scheme developed by Microsoft. Currently No technical information has been released, but it provides satisfactory sound and picture quality under low traffic conditions. The latest Windows Media Encoding Utility V8.0 pushes streaming technology to a new level. Our common ASF, WMV, and WMA are Microsoft's streaming media files. In fact, our common MPG files also have the biggest feature of streaming media - reading and playing at the same time.