wavpack: Reset internal state on corrupted blocks

wavpack_decode_block() supposes that it is called back with the exact
same buffer unless it has returned with an error. With multi-channels
files, wavpack_decode_frame() was breaking this assumption.
Signed-off-by: Janne Grunau <janne-libav@jannau.net>

libavcodec/wavpack.c

@@ -1174,6 +1174,15 @@ static int wavpack_decode_block(AVCodecContext *avctx, int block_no,
     return samplecount * bpp;
 }
 
+static void wavpack_decode_flush(AVCodecContext *avctx)
+{
+    WavpackContext *s = avctx->priv_data;
+    int i;
+
+    for (i = 0; i < s->fdec_num; i++)
+        wv_reset_saved_context(s->fdec[i]);
+}
+
 static int wavpack_decode_frame(AVCodecContext *avctx,
                             void *data, int *data_size,
                             AVPacket *avpkt)
@@ -1206,11 +1215,14 @@ static int wavpack_decode_frame(AVCodecContext *avctx,
         if(frame_size < 0 || frame_size > buf_size){
             av_log(avctx, AV_LOG_ERROR, "Block %d has invalid size (size %d vs. %d bytes left)\n",
                    s->block, frame_size, buf_size);
+            wavpack_decode_flush(avctx);
             return -1;
         }
         if((samplecount = wavpack_decode_block(avctx, s->block, data,
-                                               data_size, buf, frame_size)) < 0)
+                                               data_size, buf, frame_size)) < 0) {
+            wavpack_decode_flush(avctx);
             return -1;
+        }
         s->block++;
         buf += frame_size; buf_size -= frame_size;
     }
@@ -1219,15 +1231,6 @@ static int wavpack_decode_frame(AVCodecContext *avctx,
     return s->samples_left > 0 ? 0 : avpkt->size;
 }
 
-static void wavpack_decode_flush(AVCodecContext *avctx)
-{
-    WavpackContext *s = avctx->priv_data;
-    int i;
-
-    for (i = 0; i < s->fdec_num; i++)
-        wv_reset_saved_context(s->fdec[i]);
-}
-
 AVCodec ff_wavpack_decoder = {
     .name           = "wavpack",
     .type           = AVMEDIA_TYPE_AUDIO,