The browser main thread is responsible for DOM layout, style recalculations, garbage collection, and user input events. If network chunks or heavy video decoding run on the main thread, any JavaScript stall (even for 16 milliseconds) causes dropped video frames, stuttering playback, and visual jitter. Running VideoDecoder inside a dedicated Web Worker completely isolates video ingestion, parsing, and hardware decoding from main-thread contention. Combined with an OffscreenCanvas transferred from the DOM via transferControlToOffscreen(), video frames render directly to the screen at full hardware refresh rates without ever touching the main thread.

When VideoDecoder outputs a VideoFrame, the decoded YUV/RGB pixel planes already reside in GPU video memory (VRAM). Traditionally, converting this to an HTML5 canvas requires readbacks or CPU color-space conversions. With modern WebGPU, developers invoke device.importExternalTexture({ source: videoFrame }). The WebGPU driver creates a direct zero-copy GPU texture view pointing straight to the hardware decoder VRAM surface. A WGSL shader can sample this texture directly (using textureSampleBaseClampToEdge) with zero memory copies across PCI-e bus or CPU RAM.

VideoFrame objects represent native GPU driver handles and hardware decoder buffers, not standard JavaScript heap memory. The V8 garbage collector is unaware of the massive video memory allocated behind each handle. If an application fails to invoke videoFrame.close() synchronously in the output callback, the underlying hardware decoder buffer pool becomes exhausted after 16 to 32 frames. Once exhausted, VideoDecoder stops outputting frames entirely, causing video freezing and catastrophic memory leaks.

The decoder.decodeQueueSize property indicates how many EncodedVideoChunk objects are currently waiting in the hardware decoder queue. If network packets arrive in bursts or the hardware decoder is overloaded, decodeQueueSize increases. For real-time ultra-low-latency streaming (such as cloud gaming, drone FPV, or remote desktop), an application should monitor decodeQueueSize: if it exceeds a critical threshold (e.g. > 3 chunks), the application must drop incoming delta chunks and request a fresh keyframe (IDR) to resynchronize without accumulating latency.