Add H.264 fourcc GAVC for GeoVision cameras.

libavformat/riff.c

@@ -40,6 +40,7 @@ const AVCodecTag ff_codec_bmp_tags[] = {
     { AV_CODEC_ID_H264,         MKTAG('V', 'S', 'S', 'H') },
     { AV_CODEC_ID_H264,         MKTAG('Q', '2', '6', '4') }, /* QNAP surveillance system */
     { AV_CODEC_ID_H264,         MKTAG('V', '2', '6', '4') },
+    { AV_CODEC_ID_H264,         MKTAG('G', '2', '6', '4') }, /* GeoVision camera */
     { AV_CODEC_ID_H263,         MKTAG('H', '2', '6', '3') },
     { AV_CODEC_ID_H263,         MKTAG('X', '2', '6', '3') },
     { AV_CODEC_ID_H263,         MKTAG('T', '2', '6', '3') },