Lagarith is an open source lossless video Codec that was originally created by Ben Greenwood. It is one of few lossless video codecs and is slower then the rival Huffyuv in terms of encoding speed, but not by much.
Lagarith supports YV12, YUY2, RGB, and RGBA colorspaces in an attempt to stop rounding errors and data loss for color-space conversions.
For keyframes, Lagarith disallows inter-prediction allowing for each Frame to be separately decoded. Cutting, seeking and joining is much easier as a result.
In terms of Compression, it is also more efficient than Huffyuv.