Some knowledge about audio and video (Demux, filter, etc.)

Mux and Demux

Mux is the abbreviation of multiplex, meaning "multi-channel transmission", is actually "mixed flow", "encapsulation" meaning, and "synthetic" meaning is similar to refers to the video footage and audio footage encapsulated in a separate file.

Muxing is a verb noun form that is added to the-ing after the MUX.
Demux is prefixed with a negative de-prefix in front of the mux, meaning "decomposition multiplexing", which is the opposite of muxing, which is the part of the video or audio portion of a file that we normally call "detaching".
Similarly, it is possible to add-ing to the Demux to form the verb noun demuxing.
Meaning:
through the muxing (mixed flow), the video stream, audio stream or even a caption stream can be bundled into a separate file, as a signal for transmission, and so on, you can demuxing (separate) The inside of the video, audio or subtitles to separate the decoding and playback.
Key points:

The whole process of muxing and demuxing does not re-encode the original video, audio, or subtitles. After the mixed-flow (encapsulated, packaged) file, you can separate (decompose, unpack) operations, to obtain the same as the original footage of the independent video, audio and subtitle files.

separation and synthesis of video, encoding and decoding

There are two types of media flow processing: Encode (encoding) and decode (decoding). Coding refers to the process of translating a sound or image into a computer digital file by a certain protocol or rule. Decoding is the reverse of the code-converting the encoded media file back into a sound or image.

the software used to perform the coding is called "Encoder" (Coder or Encoder);
the software used to perform the decoding work is called a "decoder" (Decoder)
" encoder" and "decoder" collectively, "Codec" ("Codec").

sound and image are two different kinds of media, which correspond to two different senses of man. As a different medium, we can only use sound-specific software or video-specific software to analyze and process audio streams and video streams separately.

The software used to encode the audio stream is called "Audio encoder" (voice Encoder)
the software used to encode the video stream is called "Video encoder" (Encoder)

The software used to decode the audio stream is called the audio Decoder .
the software used to decode the video stream is called "Video Decoder" (Decoder)

the audio stream and the video stream must be processed separately, namely:
The audio encoder encodes a single audio file,
the "video encoder" encodes a single video file,
Audio Decoder to decode and restore audio files separately.
Video Decoder decodes and restores the video files separately.

since audio processing and video processing must be run separately, why do we usually see the RMVB, AVI format of the movie is both a sound and a single file containing the image? That's because we've not only "coded" the individual audio streams and video streams through the camera, but also "synthesized" them (Synthesis). With compositing, audio and video are packaged together to generate a separate file. It can be said that all the existing sound and image of the video files, 100% are through some kind ofSynthesizer (synthesizer)synthesized. (Note: "Compositing" differs from "merge", see the last reference post.) )

However, it is important to know that although the audio stream and the video stream can be packaged into a file by synthesizer, as the human eye cannot listen, the human ear cannot see, the audio stream and the video stream are not completely mixed together and are doomed to "separate". Therefore, the so-called "synthesis", just the audio stream and video streaming with a container file (Container) package, in fact, the inside is separate. When we play the video file, we always callseparators (Splitter), the encapsulated synthesized video is "detached" into separate audio and video streams before the decoder is called to decode the output of these independent audio streams and video streams.

For example, you should compare some of the understood:

For example we have an audio file sample.mp2 and a video file sample.m1v, with the encoding software such as the small Japan 4 by MPEG-1 encoding way to become a separate file Sample.mpg, and then put this. mpg file into the media Player to play, directly can hear the sound to see the screen. On the surface the player simply "plays" the file, and in fact this "play" contains more steps than we can see. This step is like this:

• player opens video source file
• player Call splitter to break video files into separate audio streams and video streams
• The player calls the Audio decoder to decode the audio stream while the video decoder is called to decode the video stream
• The player outputs the decoded audio stream and video stream to the playback window and keeps it in sync, based on the same time line.

we often hear Filter (filter) the name, in fact, refers to a variety of separators or decoders.

Filter (filter)

What are some of the features of HDTV that have been described in, correspondingly, to play HDTV, first to correctly unpack the package, and then to decode the video audio. So we need separators, video decoders and audio decoders, commonly known as HDTV's "three-piece set", and collectively, filters.

First, separator:
To play the multimedia file correctly, the first thing to do is to call the splitter correctly, separating the video track from the audio track. The separators are divided into three main categories.
1. MPEG2 TS Separator:
Moonlight (full name Moonlight-elecard MPEG2 demultiplexer), very good compatibility, is the preferred MPEG2 separator.
Gabest (is the MPEG Splitter), the MPC author Gabest wrote the separator.
Nvidia Transport Demux (Nvidia's own separator), is one of the members of the PureVideo family, only with the video audio decoder from the family, with N Kirby better.
2, H264 separator:
Common have gabest MP4 separator, is Mp4splitter, is also gabest writing, Halli separator and ndigital separator and so on.
3, hd-wmv separator:
Microsoft closed technology, WMP9 above all brought, XP users do not need to install.

second, video decoder
Major companies continue to develop new versions, improve image quality, improve compatibility, enhance graphics hardware acceleration.
1, MPEG2 Video decoder:
The WinDVD video decoder is intervideo to Decoder.
PowerDVD MPEG2 Video Decoder with CyberLink DTV video/sp filter and CyberLink video/sp filter
Moonlight Video Decoder, Moonlight-elecard MPEG2 Decoder is a 3.X and 4.0X version, called Elecard MPEG-2 video Decoder.
Low-end computers recommend the use of Sonic Cinemastervideo, the quality of the general, the strength is the ability to turn on hardware acceleration.
The MPEG2 video decoder in the PureVideo family is available only on cards in the N-card 6, 7 series.
Dscaler5 above said PowerDVD, WinDVD, Moonlight, Sonic and other video decoder can turn on the graphics card hardware acceleration, reduce the burden on the CPU.
2, H264 Video decoder:
The COREAVC H264 Video decoder is COREAVC DirectShow videos Decoder.
Moonlight H264 decoder, all called Moonlight H264 video Decoder,ffdshow decoder, all called ffdshow MPEG-4 video Decoder, can open n card graphics hardware accelerated CyberLink h.264/ AVC Decoder (PDVD7).
3, hd-wmv
Can only use the Microsoft own decoder, n card 6, 7 Series can turn on the acceleration.
HDTV video decoding CPU is very high, the current strongest CPU is also difficult to complete, and the CPU as a general-purpose processor, for video decoding is very inefficient, so the key to HDTV playback is the decoding speed of the display card. Whether the video decoder can support the display card hardware acceleration is the key to the ability to play HDTV.

third, audio decoder:
Ffdsshow, Moonlight Audio decoder, WinDVD audio decoder, PowerDVD audio decoder, AC3Filter audio decoder.
If you are playing an HDTV without a sound or a picture, you should start with the decoder and replace it with a try.

Some knowledge about audio and video (Demux, filter, etc.)