wavpack: Properly clip samples during lossy decode

When decoding lossy WavPack samples, they are supposed
to be clipped, in order to be decoded correctly.
Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
Signed-off-by: Ronald S. Bultje <rsbultje@gmail.com>

libavcodec/wavpack.c

@@ -110,7 +110,7 @@ typedef struct WavpackFrameContext {
     int extra_bits;
     int and, or, shift;
     int post_shift;
-    int hybrid, hybrid_bitrate;
+    int hybrid, hybrid_bitrate, hybrid_maxclip;
     int float_flag;
     int float_shift;
     int float_max_exp;
@@ -403,8 +403,14 @@ static inline int wv_get_value_integer(WavpackFrameContext *s, uint32_t *crc, in
             *crc = *crc * 9 + (S&0xffff) * 3 + ((unsigned)S>>16);
         }
     }
+
     bit = (S & s->and) | s->or;
-    return (((S + bit) << s->shift) - bit) << s->post_shift;
+    bit = (((S + bit) << s->shift) - bit);
+
+    if(s->hybrid)
+        bit = av_clip(bit, -s->hybrid_maxclip, s->hybrid_maxclip - 1);
+
+    return bit << s->post_shift;
 }
 
 static float wv_get_value_float(WavpackFrameContext *s, uint32_t *crc, int S)
@@ -792,6 +798,7 @@ static int wavpack_decode_block(AVCodecContext *avctx, int block_no,
     s->joint = s->frame_flags & WV_JOINT_STEREO;
     s->hybrid = s->frame_flags & WV_HYBRID_MODE;
     s->hybrid_bitrate = s->frame_flags & WV_HYBRID_BITRATE;
+    s->hybrid_maxclip = 1 << ((((s->frame_flags & 0x03) + 1) << 3) - 1);
     s->post_shift = 8 * (bpp-1-(s->frame_flags&0x03)) + ((s->frame_flags >> 13) & 0x1f);
     s->CRC = AV_RL32(buf); buf += 4;
     if(wc->mkv_mode)