Google Duo reaches 10 million downloads
Duo is a mobile video chat app developed by Google, available on both Android and iOS. It Was Announced at Google I / O on May 18, 2016   Alongside Allo, an instant messaging app. Duo Launched in the United States on August 16, 2016 and globally a few days later.    Quickly duo climbed to the number one free app on Google Play Within two days of Its initial release
Features of the app include: 
HD 720p video
Optimized for low bandwidth mobile networks. The app optimizes WebRTC and uses QUIC over UDP. Optimisation is further achieved through the degradation of video quality through quality monitoring network. 
“Knock Knock” – an Android-only feature qual shows a live preview of the caller Before the recipient picks up,  Which Google says is to “make calls feel more like an invitation Rather than an interruption” 
End-to-end encryption by default
Google Assistant support.
Use of phone numbers to call Easily Allow users to contact people from developer’s list
Automatic switching between WiFi and mobile data.
720p (1280 x 720 px; Also called HD Ready) signal is a progressive HDTV format with 720 horizontal lines and an aspect ratio (AR) of 16: 9 (1.78: 1). All major broadcasting HDTV Standards (Such as SMPTE 292M) Which include a 720p format has a resolution of 1280 x 720; howevera, there are other formats, Including HDV and AVCHD Playback for camcorders, qual use images with the standard 720p HDTV resolution. The frame rate is Standards-dependent, and for conventional broadcasting Appears in 50 progressive frames per second in Former PAL / SECAM Countries (Europe, Australia, others), and 59.94 frames per second in Former NTSC Countries (North America, Japan, Brazil, others).
The number 720 stands for the 720 horizontal scan lines of image display resolution (also known as 720 pixels of vertical resolution).  The p stands for progressive scan, i.e. non-interlaced. When broadcast at 60 [note 1] frames per second, 720p features the Highest Possible temporal resolution under the ATSC and DVB Standards. The term assumes a widescreen aspect ratio of 16: 9, THUS implying a resolution of 1280 x 720 pixels (0.9 megapixels).
720i (720 lines interlaced) is an erroneous term found in Numerous sources and publications. Typically, it is a typographical error in Which the author is referring to the 720p HDTV format. Howevera, in Some Cases Presented incorrectly as it is an actual alternative to 720p format.  No Proposed Permits or Existing broadcast standard 720 interlaced lines in a video frame at any frame rate.
Progressive scanning reduces the the Need to Prevent Flicker by anti-aliasing single high contrast horizontal lines.   Also It is Easier to Perform 50↔60 Hz high-quality conversion and slow-motion video clips with progressive.
A 720p60 (720p at 59.94 Hz) video has advantage over 480i and 1080i60 (29.97 / 30 frame / s, 59.94 / 60 Hz) in dry it comparably reduces the the number of 3: 2 artifacts Introduced During transfer from 24 frame / s film. Howevera, 576i and 1080i50 (25 frame / s, 50 Hz), Which are common in Europe, Generally do not suffer from pull down film artifacts or simply frames are played at 25 frames and the audio pitch corrected by 25 / 24ths. As a Result, 720p60 is used for broadcasts U.S. Often the while European HD broadcasts use 1080i50 24 * frame, with a horizontal resolution of 1920 or 1440 Depending on bandwidth constraints. Howevera, Some European Broadcasters will use the 720p50 format, Such as German Broadcasters ARD and ZDF, the Flemish Broadcasting Company (VRT) in Belgium, the Norwegian Broadcasting Corporation (NRK) and Spanish Radio and Television Corporation (TVE HD). Arte, a dual French-German-language channel produced in collaboration by ARD, ZDF and France Télévisions, broadcasts in German at 720p50 soft in French at 1080i50.
Videotelephony comprises the technologies for the reception and transmission of audio-video signals by users at Different locations, for communication between people in real-time. 
At the dawn of the technology, videotelephony phones Which Also Included image Would exchange between units still images Every few seconds over conventional POTS telephone-type lines, essentially the Same as slow scan TV systems.
Currently videotelephony has made significant usage Inroads in government, healthcare, education and the news media. It is Particularly useful to the deaf and speech-impaired WHO Can use the technology with sign language and Also with a video relay service, and well as to Those with mobility issues Computer or Those Who are Located in distant places and are in Need of telemedical or tele-Educational Services. Also it is used in commercial and corporate settings to Facilitate Meetings and conferences, between Parties That Typically Established already have relationships. Like all long distance communications technologies (Such as phone and internet), by the Therapeutic Need to travel to the bring people together Also the technology contributes to reductions in carbon emissions, thereby Helping to Reduce global warming.
Was he concept of videotelephony first popularized in the late 1870s in Both the United States and Europe, although the basic sciences to permit Its very Would take earlies Trials Nearly a half century to swear discovered. Was this embodied in the device first came to swear qual known as the video telephone, or videophone, and it Evolved from intensive research and experimentation in Several telecommunication fields, notably electrical telegraphy, telephony, radio, and television.
The development of the technology a crucial first video Started in the Latter half of the 1920s in the United Kingdom and the United States, spurred notably by John Logie Baird and AT & T’s Bell Labs. This occurred in part, at Least with AT & T, to Serve as an adjunct supplementing the use of the telephone. A number of Organizations That videotelephony WOULD BE believed superior to plain voice communications. Was howevera to swear video technology deployed in analog television broadcasting Before it Could Become long-practical or popular-for videophones.
Videotelephony Developed in parallel with conventional voice telephone systems from the mid-to-late 20th century. Very Expensive videoconferencing systems rapidly Evolved throughou the 1980s and 1990s from proprietary equipment, software and network Requirements Standards-based technologies to That Were readily available to the general public at a Reasonable cost. Only in the late 20th century with the advent of powerful video codecs combined with high-speed Internet broadband and ISDN videotelephony service did Become a practical technology for regular use.
With the rapid improvements and Popularity of the Internet, has videotelephony thru the Become Widespread Deployment of video-enabled mobile phones, plus videoconferencing and computer webcams utilize Internet telephony qual. In the upper echelons of government, business and commerce, telepresence technology, an advanced form of videoconferencing, has helped Reduce the Need to travel.
The Highest ever videocall Took place on May 19, 2013 When British adventurer Daniel Hughes used a smartphone with a BGAN satellite modem to make a videocall to the BBC from the summit of Mount Everest, at 8.848 m above sea level.
Videotelephony Can Be Categorized by Its functionality, That is intended to Its Purpose, and Also by Its method of Transmissions.
Were the earlies Videophones form of videotelephony, dating back to initial tests in 1927 by AT & T. During the late 1930s the post offices of public Established Several European governments videophone services for person-to-person communications circuit utilizing dual telephone cable transmission technology. In the present day standalone UMTS videophones and video-enabled mobile phones are usually used on a person-to-person basis.
Videoconferencing saw earlies Its use with AT & T’s Picturephone service in the early 1970s. Were analog Transmissions over short distances, soft Converted to digital forms for longer calls, again using telephone transmission technology. Popular corporate videoconferencing systems in the present day almost Exclusively have migrated to digital ISDN and IP transmission modes due to the Need to CONVEY the Very Large Amounts of data generated by Their cameras and microphones. Often These systems are intended for use in conference mode, That is by Many people in Several Different locations, all of Whom Can Be viewed by Every participant at Each location.
Telepresence systems are a newer, more advanced subset of videoconferencing systems, mean to Allow Higher degrees of video and audio fidelity. Such Typically high end systems are deployed in corporate settings.
Mobile collaboration systems are another recent development, Combining the use of video, audio, and on-screen drawing newest generation capabilities using hand-held electronic devices over secure networks broadcasting, Enabling multi-party conferencing in real-time, Independent of location.
A more recent technology is TV functions encompassing These cams. TV cams video enable people to make “phone” calls using video calling services, like Skype on Their TV, without using a PC connection. TV cams are Specially Designed That video cameras feed images in real time to another compatible TV camera or other computing devices like smartphones, tablets and computers.
Personal computer based web cameras are an unobtrusive form of videotelephony Often, usually used for point-to-point videophone calls.
Each of the systems has its own Advantages and disadvantages, Including video quality, capital cost, degrees of sophistication, Capacity Requirements transmission, and cost of use.