After receiving the file, telecom operators may do some compression according to different needs, and then send it to users through the network or IPTV.
The 4K programs of video websites are generally around 5Mbps.
Take the recent popular "Little Joy" 4K video as an example. The bit rate of HEVC encoded video files is about 5Mbps.
Take a picture for your reference:
4K video transmitted by radio and television cable TV channels, taking CCTV UHD channel as an example, occupies a bandwidth of 25Mbps:
The coding efficiency of HEVC is still very high. You know, the bandwidth of CCTV HD channel is also 25Mbps, the resolution is only 1080i, and the coding is still old MPEG2.
Of course, the original 4K video file of the camera is relatively large, but after editing and compression, the bit rate of the file has dropped significantly. Taking a video editing software as an example, the average bit rate of video used for network distribution is about 24Mbps.
The average bit rate of 50 frames is about 40Mbps.
For 4K video encoded by HEVC, the bit rate of 25 frames is also around 24Mbps under the condition of ensuring all indicators.
Then the question is, why is the bit rate of 4K video on video websites only about 5Mbps?
This is because the terminals used by website users are mostly small screens and are not sensitive to resolution. For 4K video, if the terminal size used is less than 55 inches, you can't see much difference from 1080P at all.
Due to the large video traffic and high cost, video content, video websites and even telecom and broadcasting operators used for network transmission are trying their best to reduce the resolution and code stream.
For example, the "high definition" used by radio and television operators in cable TV channel transmission refers to the resolution of 1080i; The "high definition" in the video website is used for network VOD, and the resolution may be only 1440*8 10, which is only a little higher than 720P, and the bit rate is also reduced by n times.
After using HEVC coding and optimizing various parameters, users can basically cope with the 5Mbps 4K video produced by video websites.
Conclusion: If we only watch the online 4K videos of major websites, the bandwidth at home is barely enough, and the broadband of10.5 Mbps is already extravagant.
If you use a telecom operator's IPTV to watch 4K programs directly, the default bandwidth of IPTV is 100Mbps, which is an independent bandwidth, so you don't have to worry about the bandwidth problem at all.
With the development of science and technology, many families have bought 4K TVs. How much bandwidth can support 4K video? Watching 4k TV requires about 50M bandwidth, which is calculated as follows.
1, 4K technical parameters
The corresponding resolution of 4K display is 3840*2 160.
Generally speaking, 4K can be divided into three levels, namely entry-level 4K (4K @ 30,8bit), operation-level 4K (4K @ 30, 10bit) and limit-level 4K (4K @ 120, 12bit).
2. Theoretical calculation without compression
Consider adopting the currently commonly used 4K standard, with a resolution of 3860*2 160, a data bit of 8bit/color, 3 sub-pixels per pixel (red, blue and green) and a frame number of 60fps.
Then we need to calculate the transmission rate of 4K content: 3840 * 2160 * 8 * 3 * 6012 Gbps, which is only images, and the audio track traffic accounts for about110, totaling about 13G.
Conclusion: Without compression, the bandwidth of 13Gbps is needed to transmit a 4K video.
3.H.265 compressed bandwidth
The compression ratio of H.265 standard is 350~ 1000, so the bandwidth of 4K video after H.265 compression is about 12~40Mbps.
According to the actual value, the transmission rate of 4K content field test in various countries is between 17.5~35Mbps.
To sum up, with the popularity of 4K TV, there are more and more 4K resources. Watching 4K TV content requires a stable bandwidth of about 50M. Real-time 4K video is not only limited by bandwidth, but also has certain requirements for network delay and jitter.
Some people suggest that the broadband of 10M-20M is enough, others suggest about 50M, and others say that 100M may not be able to watch smoothly. Actually, how much broadband should it be?
What is the resolution of 4K? 4K resolution is the pixel resolution of 4096 2 160. (Here's a question. We often see that some resolutions are 3840 2 160. Is it 4K resolution? In fact, the 4K resolution under the UHDTV standard is 38402160; Full aperture 4k40963112; 4K College 3656 2664. What we are talking about is that the pixel value of each row in the horizontal direction has reached 4096, which is 4096 2 160).
The standard 4K is 4096 2 160. Our current 4K TVs generally adopt ultra-high definition (3840 2 160) pixels. For example, Samsung or Sony, everyone must know. Knowing this, how much do we need?
In fact, the information content of 4K video depends on the coding format and bit rate, but the size is different under different coding or bit rate, and the general information content of 4K is twice that of 2K. If 10MB is required according to 2K, it seems that 4K needs 40MB.
However, in order to realize the smooth operation of 4K, the current broadband may not be realized. According to Ren, the network structure is not good. Huawei divides it into entry, operator and extreme, but it cannot achieve the international frame rate of 120Hz and the coding of 10-bit. The operator's 50M broadband can basically reach 60Hz frame rate and 10 bit color depth. Therefore, it can generally be about 50 m. If you want to be extreme, it is estimated that it is like gigabit broadband as netizens say.
How many megabytes of broadband do you need to watch 4K TV to ensure fluency?
Let's not talk about the broadband support required for the quality of 4k video sources. At present, the smart set-top box I use is set to 1080p HD, which meets the broadband requirements when watching movies.
Therefore, the mobile phone logs into the background of the wireless router to monitor the uploading and downloading data occupied by broadband under the IP address or iMac address of electronic equipment.
Open a high-definition movie of 1080p with the player Youku, and the instantaneous background data display takes up 3.7M bandwidth per second, which is equivalent to a broadband of nearly 40M.
After the movie is opened for 3-5 seconds, the bandwidth occupied by the movie cache is between 300 K and 500 K, that is, the network speed is 3-5 m. If it is occupied according to the broadband theory of1000 m, it is about less than 5%, and the bandwidth required to load the movie 1080p instantly is 30-40%.
There will be no video cache, and at least the network download speed between 300 KB and 500 KB should be guaranteed.
So for a 4k movie, it is twice as much as 1080p in theory. At the moment the movie opens, it needs a broadband of 50M to 60M, that is, a download speed of 5M to 6M per second, and the average cache loading needs a broadband of 1M to 2mb. Therefore, I personally suggest that if you want to watch 4K movies smoothly, you should have a broadband of at least 50M and below 100M, and it is best not to use China Mobile.
Don't say any tall terms. In a word, we are a family 169 package, with 200 megabytes of broadband and a new 4k TV, which is completely enough.
4K TV requires broadband, at least 20M, preferably more than 50 m.
1. What is a 4K TV?
4K TV means that when watching TV, the resolution of the display screen is above 3840*2 160, which belongs to ultra-high-definition, 8 times that of high-definition and 4 times that of full-definition.
With such a high resolution, the naked eye can completely see every detail in the TV picture without any pressure.
ITU stipulates that the best frame rate of 4K TV is 120Hz, and the lowest color code is 10 bit. If this standard is not met, it cannot be considered as 4K.
Second, broadband requirements.
Watching 4K TV online requires extremely high broadband.
At present, the broadband speed is still difficult to meet the requirements, so we can only adopt a compromise method, that is, after the uncompressed code is processed by video compression coding, it can be played smoothly.
The little girl did a rough experiment and opened 1080P movie Transformers on a member of a video website. The traffic monitoring software shows that the download speed is 3.7M per second, which is almost 40M broadband.
But after about 5 seconds, the speed of the movie cache dropped to about 300K to 500K, that is, about 3M to 5M, but the speed went up again and then came down again.
For 4K movies, it is twice as much as 1080P. In other words, at the beginning of a 4K movie, the broadband needs to be between 50M and 60M.
abstract
If the network is in good condition and the broadband is above 50M, the requirements of the broadcaster of 4K TV can be truly realized. If there are many smart devices at home, the bigger the broadband, the better.
Fortunately, broadband is faster now. For example, some time ago, the little girl accelerated to 200M broadband, and the 4K TV looks very cool.
Of course, if the broadband is 20M, you can watch it, but do you want to pause and wait for the cache for a while before continuing? It didn't go so well.
How many megabytes of broadband you need actually depends on the video bit rate. What is the video bit rate? Broadband is higher than this.
Working relationship, I have been exposed to a large number of 4K videos of provincial Unicom iptv with a code rate of 25m. The coding of h264. The film source is purchased in a unified way, and the national standard is also required.
Be careful not to talk about the code rate out of the coding format. Because under the same definition, different formats need different bit rates.
To put it simply, 25m of 264 mentioned above is roughly equivalent to 50m of mpeg2 or 12.5m of H265.
I can visually see that the resolution of 60 inches is not bad.
Therefore, the current reality is that the general video bit rate will not be higher than 25m, and 50 megabits of broadband will be enough.
Theoretically, the bandwidth required for watching 4K video online is usually around 12 Gbps. In practical application, the bandwidth for watching 4K video smoothly is about 50M.
Obviously, the theoretical bandwidth of watching 4K video online is far from the actual bandwidth, because 4K video data is usually compressed when it is transmitted. Next, let's talk about the calculation formula and some methods of 4K video transmission bandwidth.
The planning formula of bandwidth required for 4K video transmission is: bandwidth = horizontal pixel * vertical pixel * color depth * refresh rate.
According to the standard, the resolution of 4K video is 3840*2 160, the color depth is usually 4:4:4, and the refresh rate is 60Hz, so the calculated bandwidth is 12Gpbs. At present, the transmission of 4K video data streams is compressed before transmission, and the compression adopts H.265 standard, so the bandwidth required after calculation is about 40Mbps.
From the theoretical value of 12Gbps to the actual transmission value of about 40Mbps, this compression ratio is still very harsh. Therefore, China Unicom and China Mobile claim to provide set-top boxes supporting 4K playback. In fact, this compressed 4K is a fake 4K, which is restored by an algorithm, which is far from the real 4K local playback.
At present, a 90-minute 4K movie is about 200G, and the estimation of uncompressed 4K video is calculated by T, so the existing broadband cannot meet the requirements of play online if it is not compressed.
In short, the bandwidth required to watch 4K video online is not high, 50Mbps is enough. However, many online 4K movies are mostly fake 4K, because the compression algorithm is too harsh, and the definition will definitely be affected.
This is a very simple math problem. I simply flipped through the 4K video in my hand and found that the video with the highest video bit rate is the demo video. This is not surprising. As a demonstration video, it must show the best video effect, so the bit rate needs to be higher.
The video file size is 1.75G, and the playing time is 2 minutes 10 second. Because it is a two-channel sound, the audio code rate is ignored. Just calculate the code rate, as shown below:
1.75x1024 (2x60+10) =13.8m/s.
Because the network speed is calculated according to 8 bits, the actual display speed needs to be multiplied by 8, that is,110.4m. Obviously, the bandwidth of 100M is not enough to transmit real 4K video.
In addition, considering the loss of network transmission, at least 200M broadband is needed to ensure the stable transmission of 4K video.
It should be noted that at present, the 4K live video on the Internet is greatly compressed, and its actual display effect is even worse than that of high bit rate 1080P video. Therefore, it cannot be regarded as a true 4K video.
For the downloaded 4K movie, you can simply calculate according to my formula above, and you can know the real bit rate of this video.
This year's Spring Festival Evening, CCTV will run 8K HD transmission programs.
Traditionally, radio and television cable networks are needed. Network cable connection is required between the radio and television router and the set-top box. Instead of wireless WIFI.
Users can't watch high-definition programs with ordinary set-top boxes. At present, the highest definition at the receiving end is the 4K set-top box. Still can't meet the demand of 8 K.