A method, medium, and apparatus for encoding and/or decoding video by generating a scalable bitstream formed with a base layer bitstream and an enhancement layer bitstream, in order to provide forward compatibility, is described. The method includes reconstructing an image having an extended bit-depth and an extended video format into an image having a base bit-depth and a base video format, encoding the reconstructed image, and as a result of the encoding of the image having the base bit-depth and the base video format, generating a base layer bitstream, and reconstructing the image having the extended bit-depth and extended video format into an image having the extended bit-depth and the base video format, and by using the result of the encoding of the image having the base bit-depth and the base video format, encoding the image having the extended bit-depth and the base video format, and generating an enhancement layer bitstream with a result of the encoding of the image having the extended bit-depth and the base video format and additional data required for the extended video format.