diff --git a/libavcodec/qdm2.c b/libavcodec/qdm2.c
index 95c8c97..023fe99 100644
--- a/libavcodec/qdm2.c
+++ b/libavcodec/qdm2.c
@@ -1974,13 +1974,20 @@
 {
     QDM2Context *s = avctx->priv_data;
     int16_t *out = data;
-    int i;
+    int i, out_size;
 
     if(!buf)
         return 0;
     if(buf_size < s->checksum_size)
         return -1;
 
+    out_size = 16 * s->channels * s->frame_size *
+               av_get_bits_per_sample_format(avctx->sample_fmt)/8;
+    if (*data_size < out_size) {
+        av_log(avctx, AV_LOG_ERROR, "Output buffer is too small\n");
+        return AVERROR(EINVAL);
+    }
+
     av_log(avctx, AV_LOG_DEBUG, "decode(%d): %p[%d] -> %p[%d]\n",
        buf_size, buf, s->checksum_size, data, *data_size);
 
@@ -1990,7 +1997,7 @@
         out += s->channels * s->frame_size;
     }
 
-    *data_size = (uint8_t*)out - (uint8_t*)data;
+    *data_size = out_size;
 
     return buf_size;
 }