Support reading 64bit sgi images.

Reviewed-by: Jean First

libavcodec/sgidec.c

@@ -208,8 +208,8 @@ static int decode_frame(AVCodecContext *avctx,
         avctx->pix_fmt = s->bytes_per_channel == 2 ? PIX_FMT_GRAY16BE : PIX_FMT_GRAY8;
     } else if (s->depth == SGI_RGB) {
         avctx->pix_fmt = s->bytes_per_channel == 2 ? PIX_FMT_RGB48BE : PIX_FMT_RGB24;
-    } else if (s->depth == SGI_RGBA && s->bytes_per_channel == 1) {
-        avctx->pix_fmt = PIX_FMT_RGBA;
+    } else if (s->depth == SGI_RGBA) {
+        avctx->pix_fmt = s->bytes_per_channel == 2 ? PIX_FMT_RGBA64BE : PIX_FMT_RGBA;
     } else {
         av_log(avctx, AV_LOG_ERROR, "wrong picture format\n");
         return -1;