A bit of experience about video

Thanks to open source and non-open source of various soft phones, so that we can in the test at a very low cost and extremely happy mood, especially jitsi.

① about HD cameras.

The so-called 1080P HD camera only means that the codec capability of the camera hardware conforms to this standard.

If you want to achieve a 1080P video call, the next step is to see if the Softphone's encoding capability supports 1920*1080p.

That is: not installed on the high-definition camera, you can make high-definition video calls, but also to see the launch of a soft phone call!

② video calls can be configured asymmetrically on both sides of the resolution format.

For example, point-to-point video calls, one end set at a resolution of 1080*720 (commonly known as 720P), the other end of the set resolution 640*480 (commonly known as 480P).

As long as the terminal decoding to the end of the resolution is not a problem, this call is no problem.

Diffusion: The same HD device can be set to the appropriate resolution according to the different network bandwidth.

③ outside the door to see the MCU.

Each video hits the MCU and is re-encoded into a video parameter configured by the MCU itself.

For example, the first soft phone 720P into the MCU, the second soft phone 1080P into the MCU.

However, the output video of the MCU is configured as CIF (352x288).

Aha, you can see two-way resolution CIF Video window on each softphone.

This is the most intuitive feeling, in fact there are a lot of parameters (such as frame rate), the code rate is all processed by the MCU into a unified format.

Therefore, it is not surprising that the MCU can dynamically add subtitles to God horse.

Appendix: Some common resolutions and terminology

sub-qcif 128x96   64   QCIF  176x144       72CIF     352x288       176 1444CIF  704x576       352 288 (that's what we often say D1) 16CIF  1408x1152   704 576 The monitoring industry mainly uses QCIF, CIF, half D1 (704 x288), D1 and several other resolutions.  DCIF Resolution A more effective monitoring video encoding resolution (DCIF) is found, with a pixel of 528x384. DCIF resolution is the video image of the origin is the odd, even two half D1, by anti-interlaced transformation, composed of a D1 (720*576), D1 as the boundary processing, into 4CIF (704x576). 4CIF is reduced by horizontal 3/4, vertical 2/3, and the number of pixels converted into 528x384.528x384 is twice times the number of CIF pixels. In order to distinguish it from the commonly said 2CIF (704*288), we call it double CIF, abbreviated as DCIF. Obviously, the DCIF is more balanced in horizontal and vertical two directions than the half D1.   What is D1D1 is the standard for display formats of digital TV systems, divided into the following 5 specifications: d1:480i Format (525i): 720x480 (horizontal 480-wire, interlaced), and NTSC analog TV with the same sharpness, The line frequency is 15.25kHz, equivalent to what we call 4CIF (720x576) d2:480p format (525p): 720x480 (horizontal 480 line, progressive scan), more clear than D1 interlaced, and progressive scan DVD specifications, Line frequency is 31.5khzd3:1080i format (1125i): 1920x1080 (horizontal 1080-wire, interlaced), HD mode with the most one resolution, resolution of 1920x1080i/60hz, The line frequency is 33.75khzd4:720p format (750p): 1280x720 (horizontal 720 line, progressive scan), although the resolution is lower than the D3, but because of progressive scanning, more people on the market feel compared to 1080I (actual 540 lines) visual effect more clear. d5:1080p format (1125p): 1920x1080 (horizontal 1080 line, progressive scan), the current civil high-definition video of the highest standard, resolution of 1920x1080p/60hz, line frequency of 67.5KHZ. where D1 and D2 standards are ourThe highest standard of analog television, not known as high-definition, D3 1080i standard is the basic standard of HDTV, it can be compatible with 720p format, and D5 1080P is only professional standard.

A bit of video experience