Video playback performance test analysis
Because the test website here adopts the method of playing while downloading. Therefore, the performance of online video playback is mainly determined by the following factors: video bit rate, network bandwidth, number of online video players, video frame rate, key frames, etc. Because our video frame rate and key frames are fixed, we will not analyze them here.
Video bit rate analysis
The bit rate will directly affect the performance of network transmission. According to the bit rate definition, video bit rate = (video file size/video playback time)*8. Because the test website adopts the method of downloading and playing, if you want to make the video play smoothly, the download speed should be greater than the size of the video file that needs to be played per second (video bit rate/8). So first analyze the bit rate of the video:
According to the analysis of video producers, the ratio of video time to file size on this website is 1min: 3M. It can be concluded that the video bit rate of the video at this time is 410Kbps, so the download speed requirement for smooth video playback should be 52KB/s.
network bandwidth
In the network test, it has been found that the stable bandwidth of the server is 90mbps, so the download speed of the network should be stable to 11.25MB/s. During the file download test, according to the network throughput monitoring graph, the conclusion is basically consistent with the test results.
Network Throughput Monitoring View
Number of online players
In practice, the number of people playing smoothly online is related to the network bandwidth. A single person can play videos smoothly, which is specifically reflected in the relationship between video download speed and bit rate. The download speed is greater than or equal to (bit rate/8), and the video playback is smooth. When the download speed is less than (bit rate/8), the video cannot be played smoothly, and it needs to be paused and buffered for a period of time before playing.
In the download test, the size of the downloaded video is 21273KB. According to the bit rate analysis above, the download speed should reach 52KB/s and the video can be played smoothly. Therefore, the response is in the file download time, that is, it cannot exceed (21273/52) seconds, that is, 410s. According to the test results, video playback for about 380 people is supported at this time.
View of the relationship between the number of downloaders and download time
The figure above only reflects the number of online video players supported by the server as a purely video server. In practice, there will be other influences. For example, visiting websites and downloading related resources occupy bandwidth, and the number of online video players will decrease accordingly.
The number of online video broadcasters is not limited by system resources
The figure below shows the usage of system resources when 380 people download at the same time.
Server resource usage view
As can be seen from the above figure, except that the network bandwidth reaches the bottleneck of 100Mbps, the CPU and memory usage are extremely low. And according to the test, the read/write speed of the server disk is about 400MB/600M per second. Therefore, it can be seen that the number of online players supported by the video server is usually only limited by the network bandwidth.
in conclusion
When the video bit rate is about 410Kbps, the video server can support about 380 people to play video smoothly.
Supplementary Note
The quality of personal video playback is also limited by the network conditions of individual users.
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