How to measure QoS of GStreamer
Elements that synchronize buffers on the pipeline clock will usually measure the current QoS. They will also need to keep some statistics in order to generate the QOS event.
缓冲数据与管道时钟之间的同步通常可以用来衡量 QoS
For each buffer that arrives in the sink, the element needs to calculate how late or how early it was. This is called the jitter. Negative jitter values mean that the buffer was early, positive values mean that the buffer was late. the jitter value gives an indication of how early/late a buffer was.
每一份缓冲数据到达接收器, 元件都要计算它有多早或多迟, 这个时间差称为抖动 jitter
Jitter 为负值表示缓冲数据来早了, 缓冲数据为正值表示来迟了, 也就是说 jitter 表示了缓冲数据来得有多早或者多迟
A synchronizing element will also need to calculate how much time elapsed between receiving two consecutive buffers.
一个同步元件也会需要计算在两个连续的缓冲数据之间花费了多长时间
We call this the processing time because that is the amount of time it takes for the upstream element to produce/process the buffer. We can compare this processing time to the duration of the buffer to have a measurement of how fast upstream can produce data, called the proportion. If, for example, upstream can produce a buffer in 0.5 seconds of 1 second long, it is operating at twice the required speed. If, on the other hand, it takes 2 seconds to produce a buffer with 1 seconds worth of data, upstream is producing buffers too slow and we won't be able to keep synchronization. Usually, a running average is kept of the proportion.
我们将此称为处理时间，因为这是上游元素生成/处理缓冲区所需的时间。 我们可以将此处理时间与缓冲区的持续时间进行比较，以衡量上游生成数据的速度，称为比例。
例如，如果上游可以在 0.5 秒内生成 1 秒长的缓冲区，则它的运行速度是所需速度的两倍。 另一方面，如果需要 2 秒来生成包含 1 秒数据的缓冲区，则上游生成缓冲区的速度太慢，我们将无法保持同步。 通常，保留该比例的移动平均值
A synchronizing element also needs to measure its own performance in order to figure out if the performance problem is upstream of itself.
同步元素还需要测量其自身的性能，以便确定性能问题是否出在其自身的上游。
These measurements are used to construct a QOS event that is sent upstream. Note that a QoS event is sent for each buffer that arrives in the sink.
这些测量结果用于构建向上游发送的 QOS 事件。 请注意，每个到达接收器的缓冲区都会发送一个 QoS 事件。