ac3enc: drop a global variable

Log the warning message once per encoder instance instead.
Reviewed-by: Kieran Kunhya <kierank@obe.tv>
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: James Almer <jamrial@gmail.com>

libavcodec/ac3enc.c

@@ -1993,12 +1993,11 @@ int ff_ac3_validate_metadata(AC3EncodeContext *s)
     /* set bitstream id for alternate bitstream syntax */
     if (!s->eac3 && (opt->extended_bsi_1 || opt->extended_bsi_2)) {
         if (s->bitstream_id > 8 && s->bitstream_id < 11) {
-            static int warn_once = 1;
-            if (warn_once) {
+            if (!s->warned_alternate_bitstream) {
                 av_log(avctx, AV_LOG_WARNING, "alternate bitstream syntax is "
                        "not compatible with reduced samplerates. writing of "
                        "extended bitstream information will be disabled.\n");
-                warn_once = 0;
+                s->warned_alternate_bitstream = 1;
             }
         } else {
             s->bitstream_id = 6;

libavcodec/ac3enc.h

@@ -255,6 +255,8 @@ typedef struct AC3EncodeContext {
     uint8_t *ref_bap     [AC3_MAX_CHANNELS][AC3_MAX_BLOCKS]; ///< bit allocation pointers (bap)
     int ref_bap_set;                                         ///< indicates if ref_bap pointers have been set
 
+    int warned_alternate_bitstream;
+
     /* fixed vs. float function pointers */
     void (*mdct_end)(struct AC3EncodeContext *s);
     int  (*mdct_init)(struct AC3EncodeContext *s);