Video Quality Assurance: 9 Factors That Matter
A plethora of screens illustrating different video delivery methods
Poor-quality video streaming can turn off viewers and cause providers to lose subscribers. With robust video quality assurance, you can identify streaming issues and improve the viewing experience.
To effectively implement video quality assurance, you should track the technical factors that matter the most. They range from buffer fill and startup times to bitrate, latency, and rebuffering – and they’re all important.
Let’s talk about video quality assurance, why it matters, and the nine factors to track so you can always provide the best viewer experience.
Video quality assurance tracks the performance of the entire video encoding and delivery pipeline
Video quality assurance helps improve the streaming video experience and improve viewer satisfaction
The nine most important factors in video quality assurance are bitrate, buffer fill, lag length, lag ratio, latency, playback errors, rebuffering, startup time, and video start failure
What is Video Quality Assurance?
Quality assurance is a systematic process designed to determine if a given product or service meets predesigned quality standards. Video quality assurance applies quality assurance techniques to the delivery of video content via broadcast, cable, or over-the-top (OTT) streaming services.
Video quality assurance tracks the entire video encoding and delivery pipeline to provide the highest possible quality of experience for viewers. It measures everything from initial encoding to what viewers see on their device screens.
Why is Video Quality Assurance Important?
A recent industry survey found that 20% of OTT providers cite poor video quality as their biggest technical concern. Video quality assurance is necessary to address quality of experience (QoE) issues faced by OTT providers.
The quality of the streaming video experience is a major factor in viewer satisfaction and subscriber churn. Penthera’s U.S. Video Streaming Report found that more than half (57%) of streaming viewers will give up trying to watch a program with quality issues, and almost one-third (32%) will switch to a different playback app altogether.
According to Nielsen’s Total Audience Report, three of the top ten most important issues for viewers are quality-related: streaming/playback quality, availability across devices, and resolutions available. Only by focusing on video quality assurance can providers meet customer expectations and reduce churn.
Importance of video quality
What Are the Most Important Factors in Video Quality Assurance?
Video quality assurance tracks multiple technical factors that affect streaming playback performance. A disappointing performance in any of these areas can result in an unacceptable viewer experience.
Bitrate is one of the most important factors in video quality. Bitrate describes the number of data bits streamed per second, in terms of megabits (Mbps). The higher the bitrate, the better the video quality.
Lower bitrate content typically has a lower resolution than higher bitrate content. If the bitrate is too low, the picture becomes grainy and pixelated.
Higher-resolution video formats, such as 4K and 8K video, require much higher bitrates than standard definition or even HD video. For example, 1080p HD video typically has 8-12 Mbps bitrates, 4K video requires 35-68 Mbps bitrates, and 8K video bitrates can run up to 240 Mbps.
The downside to using a higher bitrate is that higher bitrates require more bandwidth. If bandwidth is limited anywhere in the pipeline, high-bitrate content can suffer from rebuffering issues.
OneStream Live via YouTube
2. Buffer Fill
To minimize bandwidth issues, most streaming video providers pre-load some content into a video buffer before playback begins. Buffer fill describes the amount of time it takes to fill a video’s initial buffer. A long buffer fill can affect a video’s startup time or even result in video start failure.
3. Lag Length
If bandwidth issues cause streaming speed to lag behind real-time playback, content from the buffer is used to fill in the gap until the streaming catches up again. Ideally, any lag is quickly made up so that the viewer experiences a smooth playback experience. The amount of time it takes to refill the buffer is called the lag length. If lag length exceeds the initial buffer fill, the viewer will experience rebuffering and even halted playback.
4. Lag Ratio
Lag ratio is related to lag length. It’s calculated by dividing any viewer's waiting time due to rebuffering by the total amount of viewing time. This ratio can never reach zero, due to the initial buffer fill, but providers should aim to get it as low as possible.
Latency refers to how long it takes for a frame of video to travel from the source (in live video, the camera) to the viewer. The higher the latency, the more delayed the playback.
Any part of the content delivery chain can affect latency. Every step in the process, from encoding to transporting to decoding takes time, even if it’s just a few milliseconds. It’s important to fine-tune every step in the chain to minimize its contribution to overall latency.
Latency throughout the streaming video pipeline
Low latency is especially important when watching live broadcasts, such as sporting events. Viewers don’t want to watch an important play 30 seconds or more after it occurred in real-time. For live streaming, latency needs to be as low as possible, ideally measured in milliseconds.
When watching prerecorded content, such as movies and television shows, latency is less important. It doesn’t matter as much how long it takes for a single video frame to travel from a content database to the viewer.
6. Playback Errors
A crucial factor in the viewing experience is the presence of playback errors. In terms of video quality assurance, a playback error results when playback stops after rebuffering. These errors often manifest themselves as prematurely ending videos or streaming player crashes.
Rebuffering results when streaming issues cause the video buffer to completely deplete, thus interrupting the stream. To the viewer, rebuffering can take many forms, including:
Unexpected pause in playback
Frozen audio and video
Rebuffering is one of the most common streaming quality issues. Close to half (44%) of viewers say it’s the most frustrating aspect of the streaming experience.
8. Startup Time
Filling the initial buffer takes time, as does loading content from a content library. All of this happens after the viewer presses the “play” button. If these pre-delivery activities take too long, viewers can get frustrated. For this reason, achieving short startup times is an important goal of video quality assurance.
9. Video Start Failure
Sometimes viewers press the “play” button, and the video fails to start completely. Video start failure can cause viewers to not only abandon the program they wanted to watch but also to desert the provider that’s causing them problems.
How Can OTT Providers Assure Better Streaming Video Quality?
Video quality assurance can identify delivery and playback issues, but fixing those issues remains the responsibility of the OTT provider. You can solve many video quality issues with streaming video solutions that help minimize rebuffering, startup delays, playback errors, and other problems that affect QoE and viewer satisfaction.
Contact Penthera today to learn more about video quality assurance and improving the video streaming experience.