DVI IMA ADPCM
According to the XAnim multimedia application, there are two variants of DVI IMA ADPCM, both of which are encoded and decoded with the IMA ADPCM algorithm. The original variant encodes the top nibble of a byte first, then the bottom nibble. The revised variant has the opposite encoding order.
The DVI4 codec, as defined in RFC1890 is a variant of IMA ADPCM. In DVI4 the block header stores the initial predictor state, unlike IMA ADPCM where the block header stores the first sample. Otherwise, DVI4 is decoded identically to IMA ADPCM.