qdm2: Conceal broken samples

Reported-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable@libav.org

libavcodec/qdm2.c

@@ -525,8 +525,8 @@ static void build_sb_samples_from_noise(QDM2Context *q, int sb)
  * @param channels         number of channels
  * @param coding_method    q->coding_method[0][0][0]
  */
-static void fix_coding_method_array(int sb, int channels,
-                                    sb_int8_array coding_method)
+static int fix_coding_method_array(int sb, int channels,
+                                   sb_int8_array coding_method)
 {
     int j, k;
     int ch;
@@ -534,6 +534,8 @@ static void fix_coding_method_array(int sb, int channels,
 
     for (ch = 0; ch < channels; ch++) {
         for (j = 0; j < 64; ) {
+            if (coding_method[ch][sb][j] < 8)
+                return -1;
             if ((coding_method[ch][sb][j] - 8) > 22) {
                 run      = 1;
                 case_val = 8;
@@ -579,6 +581,7 @@ static void fix_coding_method_array(int sb, int channels,
             j += run;
         }
     }
+    return 0;
 }
 
 /**
@@ -840,7 +843,11 @@ static void synthfilt_build_sb_samples(QDM2Context *q, GetBitContext *gb,
                 if (q->coding_method[1][sb][j] > q->coding_method[0][sb][j])
                     q->coding_method[0][sb][j] = q->coding_method[1][sb][j];
 
-            fix_coding_method_array(sb, q->nb_channels, q->coding_method);
+            if (fix_coding_method_array(sb, q->nb_channels,
+                                            q->coding_method)) {
+                build_sb_samples_from_noise(q, sb);
+                continue;
+            }
             channels = 1;
         }