riff: IPJ2 decodes with j2k decoder. samples can be made from mencoder and jp2avi.dll codec.

libavformat/riff.c

@@ -271,6 +271,7 @@ const AVCodecTag ff_codec_bmp_tags[] = {
     { CODEC_ID_JPEG2000,     MKTAG('M', 'J', '2', 'C') },
     { CODEC_ID_JPEG2000,     MKTAG('L', 'J', '2', 'C') },
     { CODEC_ID_JPEG2000,     MKTAG('L', 'J', '2', 'K') },
+    { CODEC_ID_JPEG2000,     MKTAG('I', 'P', 'J', '2') },
     { CODEC_ID_VMNC,         MKTAG('V', 'M', 'n', 'c') },
     { CODEC_ID_TARGA,        MKTAG('t', 'g', 'a', ' ') },
     { CODEC_ID_PNG,          MKTAG('M', 'P', 'N', 'G') },