Dynamic frame-rate selection for live LBR video encoders using trial frames

Low bit-rate live encoding and streaming of video over wired or wireless channels, as utilized in place-shifting applications, need to adapt the frame rate and bit-rate according to content and channel conditions. Typical rate control schemes work with a given target frame rate and can result in irregular frame skips that are induced by buffer conditions and quantizer saturation. Prior methods proposed to address the dynamic frame-rate selection (DFS) problem work by projecting the impact of a new frame-rate from the operating frame-rate and can have slower convergence to the required frame-rate. In this paper, we propose a scheme that utilizes a given computational capacity (typical in embedded appliances) to actually assess the impact of the new frame-rate by coding at the corresponding new frame-skip (referred to as trial frames) before committing to it. The proposed scheme offers quick content-adaptive convergence to the target frame-rate and maintains a motion-adaptive frame skipping pattern to provide a subjectively pleasing spatio-temporal quality trade-off at the operating bit-rate. In addition, the scheme can work with most existing rate control methods that operate at a supplied frame-rate and is also suitable for hooking to a user controlled quality dial.