lavc/tta: Use a safer check for encrypted streams

The user can provide a password even when the stream
is not encrypted, so check the value of s->format
instead of s->pass in ttafilter_init().
Signed-off-by: James Almer <jamrial@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/tta.c

@@ -99,7 +99,7 @@ static const int32_t ttafilter_configs[4] = {
 
 static void ttafilter_init(TTAContext *s, TTAFilter *c, int32_t shift) {
     memset(c, 0, sizeof(TTAFilter));
-    if (s->pass) {
+    if (s->format == FORMAT_ENCRYPTED) {
         int i;
         for (i = 0; i < 8; i++)
             c->qm[i] = sign_extend(s->crc_pass[i], 8);