@@ -28,6 +28,7 @@

 #include "libavutil/error.h"

 #include "libavutil/mem.h"

+#include "libavutil/intreadwrite.h"

 #include "avcodec.h"

 #include "jpegtables.h"

@@ -88,6 +89,10 @@ static int mjpeg2jpeg_filter(AVBitStreamFilterContext *bsfc,

         av_log(avctx, AV_LOG_ERROR, "input is truncated\n");

         return AVERROR_INVALIDDATA;

     }

+    if (AV_RB16(buf) != 0xffd8) {

+        av_log(avctx, AV_LOG_ERROR, "input is not MJPEG\n");

+        return AVERROR_INVALIDDATA;

+    }

     if (memcmp("AVI1", buf + 6, 4)) {

         av_log(avctx, AV_LOG_ERROR, "input is not MJPEG/AVI1\n");

         return AVERROR_INVALIDDATA;