@@ -90,7 +90,7 @@ static av_cold int decode_init(AVCodecContext *avctx)

         return -1;

     }

-    s->version_b = avctx->codec_tag == MKTAG('B','I','K','b');

+    s->version_b = avctx->extradata && avctx->extradata[3] == 'b';

     if (avctx->codec->id == CODEC_ID_BINKAUDIO_RDFT) {

         // audio is already interleaved for the RDFT format variant

@@ -134,13 +134,18 @@ static int read_header(AVFormatContext *s, AVFormatParameters *ap)

             if (!ast)

                 return AVERROR(ENOMEM);

             ast->codec->codec_type  = AVMEDIA_TYPE_AUDIO;

-            ast->codec->codec_tag   = vst->codec->codec_tag;

+            ast->codec->codec_tag   = 0;

             ast->codec->sample_rate = avio_rl16(pb);

             av_set_pts_info(ast, 64, 1, ast->codec->sample_rate);

             flags = avio_rl16(pb);

             ast->codec->codec_id = flags & BINK_AUD_USEDCT ?

                                    CODEC_ID_BINKAUDIO_DCT : CODEC_ID_BINKAUDIO_RDFT;

             ast->codec->channels = flags & BINK_AUD_STEREO ? 2 : 1;

+            ast->codec->extradata = av_mallocz(4 + FF_INPUT_BUFFER_PADDING_SIZE);

+            if (!ast->codec->extradata)

+                return AVERROR(ENOMEM);

+            ast->codec->extradata_size = 4;

+            AV_WL32(ast->codec->extradata, vst->codec->codec_tag);

         }

         for (i = 0; i < bink->num_audio_tracks; i++)