Video traces containing the sizes and (PSNR) qualities of the individual frames of a video encoding are a convenient video representation for the evaluation of video networking mechanisms. These video traces can be used to find the frame loss probabilities of a lossy networking mechanism, but can not give the PSNR video quality after lossy network transport. To date the video quality after lossy network transport could only be determined through experiments with actual video or by approximating the quality of the frames affected by a loss with some low PSNR quality. In this paper we introduce and evaluate offset distortion traces with which the video quality after lossy network transport can be accurately determined without requiring experiments with actual video. We explain how the offset distortion traces can be used by networking researchers without equipment or experience in video signal processing to accurately evaluate video networking mechanisms in terms of the PSNR video quality.