put_le32(pb, (UINT32)file_size);
put_le32(pb, (UINT32)(file_size - 8));
static int wav_write_trailer(AVFormatContext *s){    ByteIOContext *pb = &s->pb;    WAVContext *wav = s->priv_data;    offset_t file_size;    if (!url_is_streamed(&s->pb)) {        end_tag(pb, wav->data);        /* update file size */        file_size = url_ftell(pb);        url_fseek(pb, 4, SEEK_SET);        put_le32(pb, (UINT32)file_size);        url_fseek(pb, file_size, SEEK_SET);        put_flush_packet(pb);    }    free(wav);    return 0;}