avcodec/osq: avoid several signed integer overflows

Fixes: signed integer overflow: 178459578 + 2009763270 cannot be represented in type 'int'
Fixes: 62285/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_OSQ_fuzzer-5013423686287360

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/osq.c

@@ -221,8 +221,8 @@ static int osq_channel_parameters(AVCodecContext *avctx, int ch)
 #define C (-3)
 #define D (-4)
 #define E (-5)
-#define P2 ((dst[A] + dst[A]) - dst[B])
-#define P3 ((dst[A] - dst[B]) * 3 + dst[C])
+#define P2 (((unsigned)dst[A] + dst[A]) - dst[B])
+#define P3 (((unsigned)dst[A] - dst[B]) * 3 + dst[C])
 
 static int do_decode(AVCodecContext *avctx, AVFrame *frame, int decorrelate, int downsample)
 {
@@ -272,10 +272,10 @@ static int do_decode(AVCodecContext *avctx, AVFrame *frame, int decorrelate, int
             case 0:
                 break;
             case 1:
-                dst[n] += dst[A];
+                dst[n] += (unsigned)dst[A];
                 break;
             case 2:
-                dst[n] += dst[A] + p;
+                dst[n] += (unsigned)dst[A] + p;
                 break;
             case 3:
                 dst[n] += P2;
@@ -290,28 +290,28 @@ static int do_decode(AVCodecContext *avctx, AVFrame *frame, int decorrelate, int
                 dst[n] += P3 + p;
                 break;
             case 7:
-                dst[n] += (P2 + P3) / 2 + p;
+                dst[n] += (int)(P2 + P3) / 2 + (unsigned)p;
                 break;
             case 8:
-                dst[n] += (P2 + P3) / 2;
+                dst[n] += (int)(P2 + P3) / 2;
                 break;
             case 9:
-                dst[n] += (P2 * 2 + P3) / 3 + p;
+                dst[n] += (int)(P2 * 2 + P3) / 3 + (unsigned)p;
                 break;
             case 10:
-                dst[n] += (P2 + P3 * 2) / 3 + p;
+                dst[n] += (int)(P2 + P3 * 2) / 3 + (unsigned)p;
                 break;
             case 11:
-                dst[n] += (dst[A] + dst[B]) / 2;
+                dst[n] += (int)((unsigned)dst[A] + dst[B]) / 2;
                 break;
             case 12:
-                dst[n] += dst[B];
+                dst[n] += (unsigned)dst[B];
                 break;
             case 13:
-                dst[n] += (dst[D] + dst[B]) / 2;
+                dst[n] += (int)(unsigned)(dst[D] + dst[B]) / 2;
                 break;
             case 14:
-                dst[n] += (P2 + dst[A]) / 2 + p;
+                dst[n] += (int)((unsigned)P2 + dst[A]) / 2 + (unsigned)p;
                 break;
             default:
                 return AVERROR_INVALIDDATA;