1. A method for reducing a bit rate in a multimedia data stream, the method comprising: spatially filtering two consecutive frames of a first multimedia data stream, wherein spatially filtering comprises: splitting a frame into a plurality of sub-frames each comprising a two-dimensional array of sample values, the two-dimensional array corresponding to the spatial dimensions of the frame; and for at least a first sub-frame: determining an average sample value for the first sub-frame; and replacing all of the sample values in the first sub-frame with the average sample value; temporally filtering and combining the two consecutive frames to produce a pre-processed frame; encoding the pre-processed frame using a plurality of scalar quantization values to produce a plurality of encoded frames; selecting one of the encoded frames to include in a second multimedia data stream, the selection based at least in part on the visual quality of the encoded frames; and for at least a second sub-frame: determining a maximum sample value for the second sub-frame; and replacing sample values in the second sub-frame that are greater than a predetermined portion of the maximum sample value with a replacement value that substantially equals the predetermined portion of the maximum sample value; wherein the predetermined portion of the maximum sample value comprises approximately one-half the maximum sample value.