In practice, interlaced video sequences are typically coded with either a frame-only or field-only structure, irrespective of the content. However, coding in this way will not provide the best coding
efficiency. This paper proposes an adaptive picture-level field/frame coding scheme with corresponding rate control. First, a two-pass field/frame decision scheme is proposed. In this scheme, we formulate the field/frame decision as a constrained optimization problem.
The actual rate and distortion data are collected and the optimal picture-level coding decision is determined based on this data. An effective rate control for the proposed two-pass algorithm is also presented. However, since the complexity of the two-pass scheme
is relatively large since motion estimation must be performed for both the frame-based picture and the field-based picture, we also propose a one-pass field/frame decision scheme. This one-pass scheme calculates the variance of each macroblock in a field and estimates
the correlation between two fields. Based on the correlation, a decision to code the picture as a frame or as fields is made. A rate control method for the proposed one-pass scheme is also presented. Simulation results demonstrate that our scheme outperforms frame-only and field-only coding for several sequences coded at a wide range of bit-rates, and the proposed one-pass scheme obtains similar performance as the proposed two-pass scheme.