What is Jitter and How to use Jitter Buffer to reduce jitter?

Have you ever experienced the frustrating situations of instability, buffering, decreased quality, or audio-video desynchronization during video calls or while watching live broadcasts? It's understandable that you might feel compelled to refresh the page repeatedly or become disheartened and exit the application. These issues could indeed be caused by network jitter.

As professional audio-video developers, it is crucial for us to understand the causes of jitter and find solutions in order to provide users with high-quality audio-video calling services and live streaming experiences.

What is jitter

First, let's understand what data packets are. After capturing audio-video data, the sender encodes and encapsulates this data into a series of small data packets, which are then transmitted over the network to the receiver. Upon receiving the data packets, the receiver performs operations such as unpacking and decoding, and finally delivers the processed audio data to the player for playback.

In real-time audio-video transmission, due to network latency, packet loss, bandwidth limitations, and other factors, data packets may experience variable transmission speeds over the network. This can result in unstable arrival times of the packets at the receiver, leading to jitter.

Causes of jitter

Jitter is typically associated with the instability in network transmission and playback processes. Here are some possible causes of jitter:

1. Network latency: During real-time audio-video transmission, data packets may encounter varying degrees of delay while being transmitted over the network. This can result in unstable arrival times of the packets, leading to jitter.
2. Packet loss: Packet loss in the network environment can cause certain video frames to fail to reach the receiver, resulting in jitter phenomena such as frame skipping or freezing.
3. BandWidth limitations: When the network bandwidth is insufficient to support high-quality data transmission, it can result in unstable transmission speeds of data packets, leading to jitter.
4. Codec performance: The performance of the codec can also affect jitter. If the codec's processing speed is insufficient to keep up with the transmission speed of data packets, it can result in stuttering or frame skipping phenomena.
5. Player issues: If the player is unable to maintain a stable playback speed while processing video frames, it can also lead to video jitter.

Measurement of jitter

Measuring network jitter primarily involves calculating the extent of fluctuations in packet arrival times. Here are some commonly used methods to measure jitter:

1. Mean Jitter: Calculate the time difference between consecutive packets' arrival times and compute the average of these time differences. Mean jitter reflects the overall fluctuation of network latency but may not accurately describe instantaneous jitter phenomena.
2. Jitter Variance: Calculate the time difference between consecutive packets' arrival times and then compute the variance of these time differences. Jitter variance reflects the degree of network latency fluctuations, where a higher value indicates more severe jitter.
3. Maximum Jitter: Calculate the time difference between consecutive packets' arrival times and identify the largest time difference. Maximum jitter reflects the maximum fluctuation of network latency but may be influenced by extreme values.
4. Percentile Jitter: Calculate the time difference between consecutive packets' arrival times and then compute a specific percentile value (e.g., 95th percentile) of these time differences. Percentile jitter reflects the fluctuation of network latency while reducing the impact of extreme values.
5. End-to-End Delay: Calculate the total delay between the sender and receiver. This metric encompasses various factors such as network latency, processing delay, etc., providing a comprehensive reflection of the impact of jitter on communication quality.

In practical applications, it is possible to choose appropriate methods to measure jitter based on specific scenarios and requirements. Additionally, it is possible to evaluate network conditions and communication quality by combining other network metrics such as packet loss rate, bandwidth, etc.

How to Reduce jitter

Due to the real-time and temporal nature of audio and video, jitter has a significant impact on the quality of audio and video. To reduce jitter, the following technical means and strategies can be employed: