avcodec/wavpackenc: add support for encoding unspec channel layouts

Also write 0 for chmask if mask have bits outside of first 32 bits,
as wavpack does not support more bits than 32 for channel layouts.

libavcodec/wavpackenc.c

@@ -2592,7 +2592,16 @@ static int wavpack_encode_block(WavPackEncodeContext *s,
         s->avctx->ch_layout.u.mask != AV_CH_LAYOUT_STEREO) {
         put_metadata_block(&pb, WP_ID_CHANINFO, 5);
         bytestream2_put_byte(&pb, s->avctx->ch_layout.nb_channels);
-        bytestream2_put_le32(&pb, s->avctx->ch_layout.u.mask);
+        if (s->avctx->ch_layout.u.mask >> 32)
+            bytestream2_put_le32(&pb, 0);
+        else
+            bytestream2_put_le32(&pb, s->avctx->ch_layout.u.mask);
+        bytestream2_put_byte(&pb, 0);
+    } else if (s->flags & WV_INITIAL_BLOCK &&
+               s->avctx->ch_layout.order == AV_CHANNEL_ORDER_UNSPEC) {
+        put_metadata_block(&pb, WP_ID_CHANINFO, 5);
+        bytestream2_put_byte(&pb, s->avctx->ch_layout.nb_channels);
+        bytestream2_put_le32(&pb, 0);
         bytestream2_put_byte(&pb, 0);
     }