The live performance indicators that affect the visual experience are latency, freeze, and time-consuming
1. The first performance indicator of live streaming is latency
Latency is the time required for data to be sent from the source to the destination.
1 Physical delay
According to Einstein's special theory of relativity, the speed of light is the highest speed that all energy, matter, and information can reach. This conclusion sets an upper limit on the speed of propagation. Therefore, even if we feel the real time with the naked eye, there is actually a certain delay.
2 Logic delay
Because RTMP / HLS is based on the application layer protocol above TCP, TCP shakes hands three times, waves four times, and each round trip in the slow start process will add a round trip time (RTT), these interactive processes will increase the delay.
3 Jitter
Secondly, according to the characteristics of TCP packet loss and retransmission, network jitter may cause packet loss and retransmission, and indirectly lead to increased delay.
A complete live broadcast process, including but not limited to the following links: collection, processing, encoding, packetization, streaming, transmission, transcoding, distribution, pull streaming, decoding, playback. From streaming to playback, and then through the intermediate forwarding link, the lower the delay, the better the user experience.
2. The second live performance index is Caton
Refers to the frame lag in the video playback process, so that people obviously feel "card". The statistics of the number of times of playing jams per unit time is called the jamming rate.
Factors causing stutter:
1 It may be that the push end sends data interrupted
2 There may also be public network transmission congestion or abnormal network jitter
3 It is also possible that the decoding performance of the terminal device is too poor
Less or no stuttering frequency means better user experience.
3. The third live performance index takes time to be displayed on the first screen
Refers to the time after the first click to play, the naked eye waits to see the picture. Technically refers to the time it takes for the player to decode the first frame to render the display image. Generally speaking, "second on" means that you can see the playback screen within one second after clicking to play. The faster the first screen opens, the better the user experience.
The above three live performance indicators correspond to a user experience request of low latency, high-definition smoothness, and extremely fast seconds. Understanding these three performance indicators is critical to optimizing the user experience of mobile live streaming apps.
