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🧑‍🎨 | Astro Design "Private Show 2022" report.Introducing the latest video technology and products [R ...


Astro Design "Private Show 2022" report.Introducing the latest video technology and products [R ...

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The transmitter also has a built-in battery, so if you carry four on your back, even one cameraman can broadcast live.

A preview "Private Show 2022" that introduces the latest technologies and products of Astro Design will be held in 2022 6 ... → Continue reading


Wikipedia related words

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Transmitter(Soshinki) means a telecommunications device that sends out information.JapaneseThen.Radio waveOften refers to the transmitter using, and this section refers to this.Wireless communicationDescribes the transmitter in.


The transmitter isRadio ActTransmitterCalledWireless communication OfSENDForhigh frequencyEnergyTo occurapparatusAnd devices added to it "(Radio Law Enforcement Regulations, Article XNUMX, XNUMX).The receiving side of the signalReceiving machineIs.in EnglishTransmitterCalled.

A wireless transmitter is mainly composed of a circuit that generates a high-frequency signal, an amplifier circuit that increases the signal to a predetermined power, and a modulation circuit that puts information on the high-frequency signal.

In JapanRadio ActAnd its various related regulations, used for transmission equipmentRadio wave OffrequencyThe quality of radio waves such as deviation and width of radio waves and harmonic intensity is specified.Transmitters with high output火災,Electric shockBecause there is a danger such as an alarm devicePower circuitSecurity regulations such as are also stipulated.

"BluetoothDevices called "transmitters" that transmit at the user level, such as "transmitters" and remote controls for air conditioners, may also receive, but are generally called transmitters.

signal source

Oscillator circuits such as crystal oscillators and self-excited oscillators, or a combination of these, are used as devices to generate high-frequency signals required for transmission of modulated signals.PLL synthesizerThe circuit is mainly used.

Modulation circuit

Various types depending on the type of radio wave usedmodulationThe circuit is used.It is a circuit that changes the amplitude, frequency, and phase of a carrier wave by passing a signal through a modulation circuit.The various methods mainly used in analog transmitters are described below.For digital methods,Digital modulationchecking ...

Anode modulation and its variants
AM that isAmplitude modulationA method often used for transmitters.Final stage amplification element (Transistor,Vacuum tube), And the modulation signal is superimposed on the power supply voltage to change the amplitude of the carrier wave to obtain the modulation output.At the time of the vacuum tubeplateSince (anode) is used, it was called "plate modulation".It is possible to simply interrupt the carrier wave using a key operation circuit (switch) without modulation.Telegraph.
Balanced modulation
SSB-DSBThe method used for.The carrier wave is modulated by a signal wave by a circuit called a balanced modulator, but in this case, no carrier wave remains in the modulated wave.In particular, when it is necessary on the receiving side, it is possible to transmit a carrier wave by superimposing a DC voltage on the modulated signal.
Reactance modulation
FMFrequency modulationMethod often used for.Oscillator circuitReactance circuit connected to (reverse bias applied)Variable capacitance diodeEtc.) to modulate the frequency by changing the capacitance between the electrodes.
Pulse modulation circuit
A circuit that puts information on a carrier wave by changing the width and position of high-frequency pulses.

From around 2000Digital signal processingThere are also some that incorporate.

Power amplifier

A power amplifier circuit is used in the final amplification stage of the transmitter to obtain a predetermined transmission power.When amplifying a modulated wave by amplitude modulation, it is not desirable to impair the linearity of the signal, so a linear amplifier is particularly used.In the case of frequency modulation or the like, since the amplitude is constant, it is not necessary to use a linear amplifier, and power efficiency is prioritized.

Classification by modulated power (AM transmitter)

The method of performing anode modulation (or collector modulation, drain modulation) in the final stage amplifier circuit is generally called high power modulation because the required modulation power is large, and requires high power efficiency of a medium wave broadcasting station or the like. This method is especially necessary for high-power transmitters.Other methodsLow power modulationCalled.Although the latter has low power efficiency, it requires less modulation power and is often used for a simple transmitter with low power.

Typical use of transmitter

Terrestrial television broadcasting

NTSCMethod groundTelevision broadcastingThere are the following methods for the transmitter that transmits the video signal of.

Medium power stage modulation method
The final stage of the video transmitterAmplifier circuitModulate with VSB (residual sideband)filterA method that removes a part of the lower wave band (carrier frequency -0.75MHz)
Low power stage modulation method
15-40MHzIntermediate frequencyThrough the VSB filter inVHFObi andUHFA method of performing frequency conversion to a band and amplifying power

When using the same channel at adjacent transmission stations, the video carrier frequency is slightly shifted (± 10.0kHz) to reduce interference (± XNUMXkHz).Offset carrier method).

Global radar

radarMany transmittersLine pulse modulatorIs used.Other,Hard tube modulator,Magnetic pulse modulatorThere is.

Radio control

Used in wireless remote control systemsRadio control..Since it is operated by proportional control (proportional control), it is commonly referred to as a radio-controlled transmitter.PropoSometimes called.

Output notation

There are various notation methods for transmitter output, such as average power and peak power.Type of radio waveThe type to be used is determined by the type of radio station and the type of radio station.

Test items

The test items vary depending on the type of transmitter, but the following items apply in most cases.The item name is the name of the Ministry of Internal Affairs and Communications.

Related item


Streaming(English: streaming) Is mainlyvoice,MovieSuch asマ ル チ メ デ ィ アFileTransfer / playDownloadIt is a kind of method.

Normally, the file is opened after the download is completed, but when playing a large file such as a movie, it takes a very long time to download, which causes a big problem especially in live distribution.Therefore, by downloading the file and playing it at the same time, the waiting time of the user is greatly reduced.This method is often loosely referred to as "streaming".

Progressive download

Similar transfer methodProgressive downloadThere is. It is the same as streaming in that it plays while downloading the file,HTTPSince it can be transferred byVendor Lock InnStreamingserverNo need to buy,Reverse proxy,Content delivery networkThere is a big advantage that it can be delivered on a large scale at low cost, such as good compatibility with.On the other hand, unlike streaming, after playback,hard diskHowever, there was a time when the service provider avoided it from the viewpoint of copyright protection because the multimedia file remained accessible.Flash video is a typical file format that can be downloaded progressively.YouTube,Nico Nico DougaPost type such asVideo distribution siteIt is also commonly used for free content distribution. Recently, streaming technology that adds bandwidth control to progressive download has also appeared (Microsoft Smooth Streaming, Adobe Dynamic Streaming, HTTP Live Streaming, MPEG-DASH, etc.),GYAO!,Yahoo! JAPANWas adopted by[1].

Streaming protocol

Browser standard compatible protocol

  • (English edition (HLS)
    • AppleHTTP-based streaming protocol by.IETFSpecifications have been published for standardization, and many servers andclientIs supported.Also someWeb browser(Safari,ChromeEtc.) can also be played directly. Flash Player also supports playback.Also, by using a script such as hls.js,HTML5 Of(English edition It can also be played on a browser that supports the API.
  • MPEG-DASH ((English edition)
    • HTTP-based streaming technology developed by MPEG. In addition to VLC and GPAC playback support, you can also use dash.js to play on a browser that supports the HTML5 Media Source Extensions API, and use dash.as to play on Flash Player. be able to.
    • MP4Box and FFmpeg support the generation of MPEG-DASH compatible MP4 fragments.

Protocols that require plugins for browser playback

  • RTSP (Real Time Streaming Protocol)
    • It is standardized by IETF,RealMedia / QuickTime / Windows Media / GStreamer It can be played on many players, including.Also, from Flash Player, it can be played through players such as Locomote Video Player.However, many browsers do not support it directly,PluginAnd need to use an external player.
    • Most streaming software can send this.
  • MMS ((English edition)
    • Windows MediaUsed for streaming delivery of. Due to EU antitrust issues, protocol specifications including DRM using elliptic curve cryptography have been published. Many players can play MMS, but some have compatibility issues. Also, many browsers don't support it directly, requiring the use of plugins and external players.
    • Some streaming software can do this.
  • Microsoft Smooth Streaming
    • By MicrosoftSilverlightStreaming protocol for. Using HTTP progressive download technology[2].VLC media player 2.1 or later supports this playback. It can be played from Flash Player by using Smooth Streaming Plugin for OSMF. Many browsers don't support it directly, so you'll need to use a plugin or external player.
    • FFmpeg supports the generation of ISMV fragments used for smooth streaming.
  • Real Time Messaging Protocol (RTMP)
    • AdobeStreaming protocol for Flash Video by.reverse engineeringMany because the spec has been parsed byOpen source softwareCorresponds to this reproduction and transmission.However, many browsers cannot play directly and require the use of plugins.This is especially problematic for mobile devices that don't support plugins.
  • Adobe HTTP Dynamic Streaming (HDS)
    • Adobe's HTTP-based streaming protocol for Flash Video.The method of dividing the file and downloading it for each fragment is used.Many browsers do not support it directly and you need to use a plugin.
    • FFmpeg supports HDS fragment generation.

P2P multicast delivery protocol

  • Real Time Media Flow Protocol
    • It is a P2P protocol for Flash developed by Adobe, and the protocol specification is published as RFC 7016. Supports P2P multicast distribution[3].
  • PeerCast protocol
    • The protocol used by PeerCast.
  • WebRTC
    • It is a Web standard P2P API that enables P2P multicast distribution, and is directly supported by browsers. The P2P delivery protocol itself is not standardized. Chrome, Firefox, and Opera are browsers that support WebRTC.

In addition, P2P multicast distribution using Java applets is also used.

Communication path encryption

The HTTP-based protocol can encrypt the communication path by passing HTTPS instead of HTTP.

    • An encrypted streaming protocol for Flash based on RTMP and SSL developed by Adobe.Many open source software supports this playback and transmission because the specifications have been analyzed by reverse engineering.
    • RTMP and developed by AdobeDiffie-Hellman key agreementAn encrypted streaming protocol for Flash based on.Many open source software supports this playback and transmission because the specifications have been analyzed by reverse engineering.There is a flaw in the design that allows a man-in-the-middle attack.[4][5].
  • clear key
  • HLS encryption
    • Encryption using AES-128.

DRM for streaming

For streaming purposes in streaming formatCopy guardIs often provided, making it difficult to save video and music to a file. However, copyguards have been criticized for deliberately creating design flaws that narrow the viewer's viewing environment, hinder the viewer's legitimate use, and even eliminate competitor products.Defective by Design), new media aiming to be viewed on demand on any device anytime, anywhere (new media) Is often not used.


  • Google Widevine DRM
    • DRM using AES-128 CTR. Based on Common Encryption (CENC, ISO/IEC 23001-7)[6]. It can be used with MPEG-DASH. Chrome and Android support decryption. Open source Bento 4[7][8] Supports encryption. FFmpeg[9] And edash-packager and MP4BOX[10] Supports both encryption and decryption.
    • As of 2016, a problem has been found in Google's implementation of Widevine DRM[11].
  • Microsoft PlayReady
    • DRM using AES-128 CTR. Based on Common Encryption (CENC, ISO/IEC 23001-7)[6]. It can be used with Microsoft Smooth Streaming and MPEG-DASH. Decryption is supported by Internet Explorer, Windows Phone and Silverlight. Microsoft Expression Encoder, Azure Media Services samples, open source Bento4[7][8] Supports encryption. FFmpeg[9] And MP4BOX[10] Supports both encryption and decryption.
  • Adobe Primetime DRM
    • Old Adobe Access DRM. It can be used with pRTMP and PHDS. 38-bit binary for Windows after Adobe Flash Player or Firefox 32[12] Corresponds to decryption. Adobe Media Server supports encryption.
  • Marlin DRM
    • Many IP-TV support decryption. Based on Common Encryption for MP4 container of MPEG DASH and based on Marlin BBTS for MPEG2-TS container of MPEG DASH[13]. Open source Bento 4 supports encryption[7][8].
  • OMA DRM v2.0
    • Many feature phones support decryption. DCF and PDCF exist in the file format[14]. PDCF is based on 3GPP PSS[14]. Except for syntax(English editionCompatible with[15].


These are legacy, and Hollywood Studios (excluding Disney) is promoting DRM for Ultra Violet.

    • DRM using elliptic curve cryptography. It can be used with MS-RTSP and MMS. Windows Media Player and Windows Phone support decryption. Windows Media Rights Manager (WMRM) supported encryption.
    • With the Windows 10 Anniversary Update, WMDRM decryption has been removed, making it impossible to watch media encrypted with WMDRM[16].
  • Helix DRM
    • Can be used with RealRT SP. Real Player supports decryption. Helix Universal Server (Discon[17]) Supported encryption.
  • Fairplay
    • QuickTime Player supports decryption. 2016, Microsoft Azure supports FairPlay encryption[18].

Main streaming server

Currently, with the spread of HTTP-based streaming protocols, it is becoming mainstream to fragment videos and send them on HTTP servers.

  • Adobe Media Server (Formerly Adobe Flash Media Server (FMS))
    • A streaming server for Windows and Linux provided by Adobe.Today, it was the only way to deliver copy-protected videos to the most popular multi-platform Flash Player on PCs.De facto standardIt has become. It also supports distribution to iOS, which cannot use Flash Player, and can be played from a browser by using the Protected HLS protocol.Similarly, for distribution to Android 4.1 or later, which cannot use Flash Player, it is necessary to install the Adobe Air application on the playback side.To use copy guard, you need to use the professional version or higher.Since there are license restrictions on the maximum number of simultaneous connections and the number of processes depending on the version, it is necessary to purchase multiple licenses for one server and stack the licenses for large-scale distribution.
  • Wowza Streaming Engine(Formerly Wowza Media Server)
    • A video streaming server developed by Wowza Media Systems. Although it can communicate with Adobe Flash Player using RTMP, it also supports remote procedure calls between client and server, in which case the server side is written in Java. From version 4.0, it is equipped with a GUI that can be managed on a web browser basis.
  • (English edition
    • A multi-platform streaming server for open source Flash Player written in Java.The license is Apache License 2.0 (changed from LGPLv3). It supports not only video distribution by RTMP and encrypted video distribution by RTMPE, but also Flash shared objects and Remoting.However, the programming language is Java, and server-side scripts written in ActionScript for FMS cannot be run directly.
  • (English edition
    • An open source streaming server based on NGINX. It supports not only RTMP but also live streaming by HLS and MPEG-DASH.
  • SHOUT cast
    • WinampIs known as the development and distribution destination ofNullsoftWas provided free of charge, but was acquired by Internet radio station Radionomy.
    • Platforms from Windows 95/98/Me/NT/2000/XP/2003 to FreeBSD, Linux,MacOS A wide range of servers, Solaris 2.x servers (Sparc version) and supported OSbinaryIt is distributed in.
    • MP3Format data can be transmitted by streaming. In addition, you can perform live transmission by combining the plugin installed Winamp and SHOUTcast server.
  • Icecast
    • MP3An open source streaming server capable of streaming formats.
  • VLC media player (Video LAN Client)
    • An open source multimedia player developed by the VideoLAN project.GUIだ け で な く,INIt also has a web interface and supports streaming. Streaming output is possible with protocols such as HTTP, MMSH, RTSP, and Icecast.

Major development-stopped streaming server

  • Helix Universal Server
    RealServer's successor product,Real networksWas on sale. Discon[17].. The media types that can be distributed are Real Media, Windows Media,Quick TimeThere are abundant and OS types as platforms are Windows NT, Windows 2000,Linux,FreeBSD,Solaris,HP-UXAnd so on.
    It does not support copy protection of other companies' products. Although it has its own copy guard, Helix DRM, it is rarely used because it can only be viewed with Real Player. In addition,Real networksAlthough the player has developed Harmony technology to support copy protection of other companies' products in order to ensure DRM interoperability, it has stopped development due to possible lawsuits from Apple.
  • Helix DNA Server
    An open source version of Helix Universal Server developed by Real Networks. It applied its own license. The final version is 2006 released in 11.1.
  • VLS (Video LAN Server)
    An open source streaming server developed by the VideoLAN project. Currently, most of the VLS functions are also implemented in VLC, and development of VLS has been completed.
  • Darwin Streaming Server
    An open source streaming server.
  • QuickTime Streaming Server
    OS X ServerStreaming server installed in.
  • rtmplite
    An open source streaming server for Flash Player written in Python. The license is GPLv3.
  • C ++ RTMP Server
    An open source streaming server for Flash Player written in C++. The license is GPLv3.
  • PeerCast
    An open source streaming system using P2P technology. It has no transmission function and has only a relay function. It supports RTSP and MMS relay.
  • FFserver
    FFmpegAn open source streaming server included in. It was compatible with HTTP and RTSP. Abandoned[19].
  • IIS Media Services
    MicrosoftIt is a streaming server for Windows provided by(English editionSuccessor product of. Encoders for content development are distributed free of charge. It is difficult to deliver videos with copy guard enabled to PCs and mobile devices other than Windows because they cannot be viewed on other than Microsoft products.
    Not updated and requires workaround for installation on Windows Server 2016 or later[20].

Main fragmentation software

  • MP4 Box
    It supports the generation of MPEG-DASH compatible MP4 fragments and MPEG-DASH compatible MPEG-2 TS fragments. Open Source.
  • FFmpeg
    It supports the generation of MPEG-DASH compatible MP4 fragments, MPEG-DASH compatible WebM chunks, HDS fragments, and ISMV fragments used for Microsoft Smooth Streaming. Open Source.
  • edash-packager
    It supports the generation of MPEG-DASH compatible MP4 fragments. ISO Common Encryption and(English editionWidevine DRM encryption/decryption, which is one of the above. Open Source.
  • TITAN File
    ATEME video conversion software. It supports MPEG-DASH, Smooth Streaming, and HLS compatible fragment generation.


  • Amazon Elastic Transcoder
    Supports MPEG-DASH, Smooth Streaming, HLS[21].
  • Azure Media Services
    Supports MPEG-DASH, Smooth Streaming, HLS[22].
  • Akamai Media Services Live / On Demand
    Supports MPEG-DASH, Smooth Streaming, HLS, HDS[23][24].
  • Arkena Cloud4TV

Major web-based streaming media players

HTML5 and Flash based web player. Open Source.
HTML5 and Flash based web player. Open Source.
HTML5 and Flash based web player. Open Source.
Shaka Player
HTML5-based web player from Google. Open Source.
Strobe Media Playback
Flash-based web player from Adobe. It is based on OSMF (Open Source Media Framework). Open Source. Updating is stopped.
For OSMF, Microsoft has released Smooth Streaming Plugin for OSMF that supports Smooth Streaming.
Locomote Video Player
Flash-based web player. Open Source. It also supports RTSP.

Live streaming

Live streaming (en: Live streaming) Is to stream live media. More specifically, computerized (live) media recorded on the fly.networkReal-time streaming delivery via (Live distribution). The following are examples of live-delivered media.

Live streamingLive broadcast (en: Live broadcast) Is considered.インターネットLive streaming, which is a live broadcast usingRadio waveComplex broadcasting such as TV media usingAuthorizationNo procedure / examination / acquisition required.Therefore, it is possible to open pseudo radio broadcasting and TV broadcasting on the net.IndividualAnd small varietyCorporationGroup, existingRadio station(Broadcasting on TV with live camera images in the studio of the broadcasting station) is also actively participating in live streaming.As mentioned above, (of broadcast contentCopyrightThere are almost no regulations (as long as the relationship is cleared)Media formTherefore, if you prepare the equipment刑 務 所It is also possible to relay to the inside of the network.

The disadvantages include the following.

  • In the case of live streaming, it is possible that the viewer forgets the broadcast time and misses the target program, as with existing broadcast media.
  • As a common drawback of live streaming and non-live streaming (streaming transmission of on-demand contents without restrictions on broadcast time), when setting the image quality specifications on the Internet TV broadcast side, priority is given to the acquisition of many viewers (low specification). I am worried about whether or not to reduce the image quality, image size, and number of video frames so that I can withstand viewing even on a PC or a PC connected to a low-speed narrowband communication line.

Delivery platform

There are various livestreaming platforms.

Live streaming transmission

Adobe Flash Media Live Encoder
Open Broadcaster Software (OBS)
Open Source.
(English edition ((English edition)


[How to use footnotes]
  1. ^ 9 Special Interview-Ask Yahoo, Why Silverlight
  2. ^ About MSDN IIS Smooth Streaming
  3. ^ Media Multicast (RTMFP) Adobe
  4. ^ Ripping Media Off of the Wire A Step-by-Step Guide P.40 DEF CON 2010
  5. ^ What is RTMPE Wowza Media Systems
  6. ^ a b Using PlayReady and / or Widevine Dynamic Common Encryption Microsoft
  7. ^ a b c Software DASH Industry Forum
  8. ^ a b c MPEG-DASH Axiomatic Systems
  9. ^ a b FFmpeg Changelog
  10. ^ a b Common Encryption GPAC project
  11. ^ A Bug in Chrome Makes It Easy to Pirate Movies Wired June 2016, 6
  12. ^ How to watch DRM content in Firefox#Supported environment Mozilla Support
  13. ^ Marlin Tutorial Intertrust
  14. ^ a b OMA DRM standardization trends NTT DoCoMo
  15. ^ OMA DRM GPAC project
  16. ^ Windows 10 Anniversary Update: Music and Video Loss Microsoft
  17. ^ a b Helix Media Delivery Platform RealNetworks
  18. ^ Microsoft announces general availability of Apple FairPlay Streaming for Azure Media Services MSPoweruser August 2016, 8
  19. ^ ffserver program being dropped FFmpeg project July 2016, 7
  20. ^ Workaround: error installing IIS Media Services on Windows Server 2016 Microsoft May 2017, 5
  21. ^ Amazon Elastic Transcoder now supports MPEG-DASH Amazon May 2016, 5
  22. ^ Azure Media Services overview and common scenarios Microsoft
  23. ^ Media Services Live Akamai
  24. ^ Media Services On Demand Akamai

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