lavf/aiffdec: don't stop parsing after SSND chunk

Some file has ID3 chunk placed after SSND.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/aiffdec.c

@@ -259,7 +259,7 @@ static int aiff_read_header(AVFormatContext *s)
             offset = avio_rb32(pb);      /* Offset of sound data */
             avio_rb32(pb);               /* BlockSize... don't care */
             offset += avio_tell(pb);    /* Compute absolute data offset */
-            if (st->codec->block_align)    /* Assume COMM already parsed */
+            if (st->codec->block_align && !pb->seekable)    /* Assume COMM already parsed */
                 goto got_sound;
             if (!pb->seekable) {
                 av_log(s, AV_LOG_ERROR, "file is not seekable\n");