1. A method for encoding a video stream using a computing device, the video stream having a sequence of frames, the frame having blocks formed of pixels, the method comprising: storing a reference frame identifier with a reference buffer index for each of a plurality of reference frames after encoding a first frame of the sequence of frames; updating the plurality of reference frames by updating a reference frame associated with a reference frame identifier after the storing; determining multiple candidate motion vectors for a current block of a second frame after the updating, the multiple candidate motion vectors including a first motion vector used to predict a collocated block within the first frame; performing a motion search for the current block within a reference frame of the plurality of reference frames, after the updating, to generate a second motion vector; comparing the reference buffer index stored with the reference frame identifier of the reference frame associated with the first motion vector to a reference buffer index of the reference frame used in the performing; and on a condition that the reference buffer index of the reference frame used in the performing matches the reference buffer index stored with the reference frame identifier of the reference frame associated with the first motion vector, advancing the first motion vector ahead of remaining ones of the multiple candidate motion vectors for encoding the current block.